There seems to be some cognitive dissonance taking place in some people's heads here. On the one hand, Europe is useless and we don't need their help. On the other, we actually do want their help but Europe is being selfish. Furthermore, people think that Europe and America have been too focused on European affairs (such as Ukraine), and this is unfair for America, so America should focus on its own interests and Europe do likewise. Which is actually a reasonable position with plenty of merit. But then when America pursues its interests (Iran) and Europe pursues its interests (Ukraine), now suddenly we need the old alliance back in action and if America goes to war with some random sand people country, Europe needs to go with them, otherwise they are "bad allies". Even though separate strategic focuses for each half of the alliance was America's idea.
There's alot of really good points in your post so I'll try to drill down on a few of them. I think you're very right about Europe having a somewhat chaotic and inconsistent reaction, and I think it ties into the US' underlying frustrations. I don't think you can look at this issue in a vacuum, and alot of these reactions are rooted in existing frustrations with our current relationship.
There is this notion that US and EU interests are aligned and it is becoming increasingly apparent that this is no longer the case. I don't think Europe is being asked to participate because we seriously need their contributions, I think they are being asked to participate as a test of their reliability as a partner. I think in many cases it is less that Europe is being selfish, and more that they take their position for granted, and don't realize what is needed to keep a healthy alliance. If Europe had little participation, but was vocally supportive of the US, strayed out of the way, let the US borrow their bases, etc. I think they could get away with a weaker military involvement. They would have a clear place as a useful ally who wasn't a superpower but wasn't obstructive. This isn't the case though, and Europe spends alot of time acting like they should be involved, without the contributions to back it up. This is exacerbated by the slow moving processes they have implemented, which makes it difficult to move in a timely fashion, which is very problematic for the US, which wants to operate fast and ensure that its place as the top world superpower is secured.
In Europe's case, I think there is an internal identity crisis that is a part of the issue too. When the US threatened to cut all trade from Spain, the EU said that we need to operate through them instead of with individual member states. However, that was a retaliatory measure against Spain's own actions. If the US isn't supposed to negotiate with individual member states, why are they able to impede US operations of their own volition. Is the EU a single entity, or is it a group of independently operating nations? That needs a clear answer, and the answer can't be a giant longwinded meeting in Brussels, because these are serious problems and action has to be swift.
The US and the EU need to sit down and have a serious discussion about what the future relationship looks like. The relationship has been too off-balance and has led to frustrations. They move at different speeds, and that doesn't work for certain types of situations. Europe, perceived as a dependent without contribution, has a tendency to countersignal the US on global issues. If they were more publicly supportive, even if they contributed less in regards to resources, there would probably be less strain on the relationship.
