In order.
Probably, but it’s been dying since the end of the Cold War and I have long advocated Europe taking back control of its defence and security as the US serves its own interests first and everyone else’s second. That is not a criticism of the US. All countries do.
NATO is not an active form of ‘American imperialism’. It is a projection of American power, but primarily a defensive one. That countries seek to join NATO is as much about the behaviour of one country in particular and its recent oppression of those countries. Russian imperialism is an actual thing that drives NATO recruitment.
The American presence in Europe has waned since the end of the Cold War. If we see a mutual interest in having a US base here, then I don’t have an issue. The UK should judge these matters in what benefits us first and foremost.
I think a lot of countries, especially those in an Eastern Europe definitely feel safer. I can guarantee that Ukrainians would definitely not only feel safer, but be safer right now.