The problem is, America's NATO war guarantee is wrapped up in a larger ideological status quo across the West. Trade liberalization, political liberalization, increased migration, sexual and cultural liberation from Christian traditionalism, the further political integration of the E.U., and the expansion of the Western alliance to the borders of Russia are all wrapped together in the minds of policymakers. And so, every reversal for any part of that project is seen by the guardians of the policy consensus as a demoralizing reversal for the Western alliance and, consequently, a gain for revisionist Putinism.The international institutions that have been left to us have evolved from a certain set of geopolitical circumstances and partake of certain policy presumptions. It seems (to me at least) that many of these institutions have done considerable good, but the question before us isn't whether they've done good in the past but how to preserve and revise these institutions so that they can do good in the future.
That's one of the major reasons why ideological nostalgia has been so toxic for the enterprise of looking forward for both foreign and domestic policy. This nostalgia has made many current leaders resistant to--and perhaps even ignorant of--the fact that we no longer live in 1989. For instance, for years, public skepticism about the European Union has been simmering throughout Europe. And yet policymakers nevertheless plunged ahead with an integration that became less and less tenable as time went on. And now many of these policymakers are now shocked, shocked that some voters might be having second thoughts about the "European" project. Taking a more moderate approach to integration (especially in terms of immigration and currency.) and responding more to immigration could have helped solidify the EU. Instead, a reckless integration threatens breaking it apart.
The importance of attention to present-day realities has implications beyond the EU, of course. In defending international institutions, policymakers need to think of the world not as it was or as they would like it to be but as it is.
We can have either a robust international order or ideological nostalgia--but not both.