First of all,
it's been noted since 1998 by people far smarter than me that "NATO-without-Russia" is basically asking for an eventual showdown with Russia. To be fair to NATO leadership, there
were talks about post-Soviet Russia joining NATO with Boris Yeltsin, but Yeltsin thought NATO was too US-centric and backed out. There were also talks between Bill Clinton and Putin about the Russian Federation joining NATO, but Putin backed out. Putin wanted the NATO to invite Russia, not have Russia apply, and he also had the same concerns as Yeltsin about NATO being basically a US-directed military alliance... which it is.
They were ok with the IMF and the World Bank and the UN, all of which are fundamentally US-directed institutions. Russia wants military hegemony over Europe or no deal, this position isn't something that the US can sell to Europe, it's not a cost Europeans want to bear. Russia doesn't want to be a junior partner, it wants to leverage its only two assets, Soviet military surplus and lots of oil and gas, and get dominion over a continent and a half. It's not a great deal for anyone but Russia.
Second of all, it's basically a US-subsidized military defense organization. The US pays the lion share in terms of money, materiel, and manpower. European countries slack off by and large. Countries that border Russia, Greece, and the UK actually meet their contribution requirements, but everyone else is a leech.
They became 'leeches' after the general peace achieved in 91, which didn't truly end until 3 years ago. They're still creditors to the US--the ECB holds a shitload of treasury securities. They're a big part of the funding of our military adventures and a big part of the cost basis for our military, and our best secondary customers for our defense contractors. They didn't have a defense budget because frankly they didn't have much of a defense need, and the US found many pressing war needs that they didn't.
This wouldn't be so bad if the Europeans were in any way grateful towards or cooperative with US foreign policy, but they are neither. If Russia invaded tomorrow I think the Europeans would immediately scream for the US to come save them, but the question begs: why the fuck are we subsidizing a bunch of people and countries who hate us? Why are we defending people and governments that openly conspire against us while enacting tyrannical policies upon their own people?
Europeans do, unfortunately, still govern themselves and our empire is largely an empire of arrangements, institutions, and somewhat formal levers of international policy. I would prefer an American World Empire, if only for conceptual simplicity and for the reimposition of liberalism and liberal government on fundamentally illiberal and backward peoples like Europeans. They've betrayed their potential out of resentment and fear of tragedies repeating themselves, thus locking themselves into a cycle of tragedies.
We are subsidizing their defense needs because they provide a large part of our trade needs, they provide a large market for our goods, they are creditors and historic allies to the US. Breaking military alliances should not be made on a "last 10 years" kind of perspective but a "last century" and "next 20 years" kind of horizon. Not how are they acting today, but how are their strategic and political interests actually aligned particularly when push comes to shove. If they actually need us, that is a shitload of leverage in the negotiation room, as Trump has continually demonstrated. You ought to consider the reality that politics is messy, that negotiations are tricky and largely private, and that objective reads of security and economic interests are pretty good weathervanes where cultural and local political forces simply aren't indicative of how things are.
The problem is when your vassals forget the arrangement, act entitled, and basically invite the invaders into their countries (Muslims, Russian energy interests, etc). The EU being a bunch of retarded communists is a feature, not a bug.
Russian energy interests have fueled the European economy since World War 1. Oil price collapsing after the OPEC embargo and the US-OPEC alliance under Reagan killed the Russian economy more than anything. The Europeans are not really our vassals, they have large amounts of freedom of action and strong endogenous incentives to do and say what they want, even if it is wrong. If their governments are evil it only reflects the fundamental character of those people. Europe falling under the sway of a moralizing, godless, suicidal ideology based in a bastardized and hyperpoliticized form of Christianity is their history and their destiny since the days of Constantine.
Even if in the starkest military reality they 'must' do as they are told, except of course for some reason there's not a lot of gun-to-the-head negotiations in Brussels. Why? Because that shit works once or twice before you are undermining your own power base. Europe technically
does have options if the US forgets long-term interests and how to do diplomacy in favor of direct coercion against allies. They're not great options, but neither is the gun to the head. Coercion is not universally effective, and as any person who knows anything about Europe could tell you, vassalage was an extremely fragile, easily gamed and constantly abused system. If the king tells you "bring me 2000 men" you send him 200 and tell him that's all the men, there was a horrible famine or plague or the bandits got the men. When the king goes off on his expedition, you start raising a ruckus because fuck taxes and fuck this distant bastard taking your money and your men.
Your incentives are
never actually aligned to comply with demands done under threat of arms, you temporize, you lie, you evade obligations as much as possible. Retarded kings making crazy-sounding demands on faithless petty lords--this is the only story arc of feudalism's 1000 year history. It was not stable, it just didn't collapse because feudal oaths were infrequently honored. It was just never capable of building up existential threats to itself because of how inefficient it was and how faithless a local baron could be.
If your model of the US system of alliances is vassalage--then there's a good answer for why the vassals are bitchy, petty, and not interested in following the leader and risking their necks. Fealty is not some ironclad bond that compels action, it occasionally directs you to act against your interests, in the minimal fashion you can tolerate.
