Why do some societies, like some couples, fall apart under pressure, while others band together? If a crisis brings them together, will that make them stronger in the future? And if they come apart, is that a sign that they should never have been together in the first place?

This week's exemplar for "banding together" is the European Union, whose leaders agreed to extraordinary new measures to promote a broad economic recovery in the wake of the novel coronavirus. The agreement represents an about-face from the stance the EU took in the wake of the financial crisis of the last decade, which emphasized austerity rather than stimulus. More importantly it broke two key structural taboos: the European Commission will, for the first time, be authorized to borrow significant sums of money; and a large portion of that sum will be disbursed to member governments in the form of grants.

Those structural changes set a precedent that could be a foundation for a much stabler European governmental edifice. A key problem with the setup of the EU has been that it is a monetary union with no comparably unified fiscal policy. As a consequence, in times of recession, member states are constrained (much as individual American states are) by their inability to print money or to run up unlimited debt — but they had no equivalent to the federal government to turn to for fiscal assistance. Now, they do.

Moreover, because the debt is being incurred at the level of the European Commission, the agreement creates pressure for further fiscal integration — particularly in the form of Europe-level taxation. If the EC wants to avoid endless squabbling among member states about how to share the burden of repayment, it will need the authority to levy taxes on its own. And that's the kind of authority of which states are built. The deal may not have been a "Hamiltonian moment" — there are many hedges included to placate northern-European member states who were reluctant to write blank checks to Italy and Spain — but it is a meaningful step down Hamilton's road.

This is a notable turnaround, not only from the response to the financial crisis but from the situation only four months ago. At that time, some commentators (including myself) wondered whether the manifest lack of intra-European solidarity on display in the face of the virus — only 21 percent of Italians felt at the time that membership in the EU was beneficial — might not deal the Union its final death blow. How did things change so much so quickly?

The simple answer is that France and Germany were in broad agreement on what needed to be done, and that when the two giants of the EU agree it is difficult to build a blocking coalition. One might also say that even the most reluctant member states understood that this is a time when, if they did not hang together, they would surely hang separately.

But, in fact, they did not all hang together. One key member, the U.K., had formally walked out only in January, just as the viral storm was breaking.

That departure was not irrelevant — and may even have been dispositive. The U.K. was a large and strong European member state particularly disposed to guard its own sovereignty, and hence to resist efforts toward ever-deeper union. Had it been in the room, the historic deal would have been much less-likely to happen. But it's possible that the deal would never even have been on the table because, with the U.K. in the EU taking stances congenial to the German financial class, Germany's own political calculus might not have shifted as it did. Merkel might have inclined less toward unity with France, and more towards the "frugal" states like Austria and the Netherlands, much as Germany did during the aftermath of the financial crisis.

In the immediate aftermath of the Brexit vote, I argued that while leaving was a very risky move for Britain, it was almost certainly a good one for the future of the EU as an institution. This is the first event that suggests that view might have been correct. And it suggests a lesson: that if you want a political union to succeed, its major components need to agree on the essential nature and purpose of that union. Papering over fundamental differences may work in normal times, but in a crisis they can tear the union apart. And restoring that sense of common purpose may require reducing rather than expanding the union's scope.

Which brings me to the union that seems to be coming apart: our own.

The primary characteristic of the American response to the coronavirus has been its disjointedness, indeed, the lack of any national policy to speak of. Individual states have been responsible for setting up their own testing infrastructure and contact-tracing apparatus, setting their own policies with regard to non-pharmaceutical interventions from lockdowns to mandatory masking, and even placed in competition with one another for personal protective equipment. Our federal system does give the states substantial authority and responsibility in these areas — but it does not require the federal government to be as derelict as it has been in either building essential common infrastructure or promoting an agreed upon set of best practices. It certainly doesn't require the federal government to use its leverage punitively, refusing, for example, to provide necessary funding to facilitate the opening of schools, and then threatening districts that don't open with financial ruin.

Much of the failure at the center of national power can be laid at the feet of President Trump, who has evinced a complete lack of interest in wielding that power to achieve meaningful collective goals, even those he ostensibly favors (like building a wall with Mexico). But Trump is interested in using power for pure assertion of prerogative, as he has demonstrated through his abuse of the pardon power and, most recently, by sending federal agents to Portland in response to ongoing protests and damage to federal property. The purpose of his intervention, as my colleague Damon Linker has noted, is precisely to create the very chaos that he claims to want to quell, on the theory that public disorder ultimately helps the candidate promising a strong hand. But it is also intended to demonstrate a willingness to use force against those who, in the view of his core supporters, deserve such treatment.

The consequences to national cohesion of this approach to federal governance — neglect coupled with brutality — are likely to be felt long after this administration has ended. A progressive prosecutor in Pennsylvania is already on record as saying he will order the arrest of federal agents if they break the law in his jurisdiction, as they did in Oregon. Even if he never has to make good on that threat, a line has been drawn, and the prospect of direct confrontation between state and federal authorities in some future contingency is real. Meanwhile, states (such as in the northeast) that banded together to combat the coronavirus, and that are now requiring visitors from the rest of the country to quarantine upon entry, will undoubtedly find new ways to work together without waiting for the federal government. The more successful they are, the less it will seem worth it to spend the energy trying to work with parts of the country that see things too differently. It is not only other countries that have reason never to trust America again; our own citizens have every reason to doubt whether an evanescent national majority can truly be counted on.

Joe Biden's presidential campaign is substantially premised on the notion that such a majority would not be evanescent. Trump has finally united the center of the country against him, and a decisive repudiation will restore Americans' faith in the possibility of collective action. The first part may prove true in November, but I wonder about the second, and not only because I remember how quickly the overwhelming Democratic majority of a dozen years ago curdled into endless partisan trench warfare. The main Democratic answer to how to avoid a repeat, after all, involves a willingness to break some norms of their own, but the centrifugal forces of American political life cannot be arrested by manipulating the composition of the Senate or packing the Supreme Court, however theoretically justified those moves might be.

Is there any alternative? One piece of advice you'll often hear in couple's therapy is to take the possibility of a breakup seriously, not as a threat but as an option. People who feel trapped don't make the best negotiators. But once the possibility of an exit is real, rather than a desired fantasy, its costs and possible benefits can be more rationally weighed against other options, including renegotiating the terms of the relationship.

In that spirit, perhaps it behooves all of us who are appalled by the Trump years, and by what has happened to the party he purports to lead, to devote at least some of our energy to thinking outside the box. How much do we actually want our states and cities to depend on the federal government, versus how much freedom do we want to chart our own course? Do we want the battle against climate change to depend on which party controls the EPA — or do we want California to be able to use its economic clout to muscle the rest of the country along? Even less-realistic fantasies of separation could prove constructive. Calls for a Calexit — or a Texit — right now are little more than tantrum threats. If they became more realistic, though, they could concentrate the mind wonderfully. Or they could reveal a reciprocal willingness to let go that would be foolish to ignore.

It would be far better if we managed to come together. But if we can't, it's worth asking ourselves not only how to seize precarious control of the levers of national power, but where power can be held securely, where the center still might hold, and what economic and political arrangements might enable those areas best to thrive. As for those who seem to be motivated primarily by spite towards their foes, where they constitute a majority, it might be worth thinking about how to let them go their own way, rather than clutch them ever tighter in an ever more imperfect union.

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