> What is the European alternative to the US military if Russia attacks Europe?

European military. Why do some people act as if European countries had no armies?

And even if we had no armies and Russia attacked and totally destroyed us, how is it related to the topic discussed here, which is whether the influx of European engineers to the US will continue or not?

> This whole thing just seems like the standard hysterical overreaction of people who spend too much time on social media.

Perhaps. I don't think it is, but let's say you are right. How is that relevant? People do not want to go to a country they perceive negatively. Whether that perception is an objective fact or hysteria is, in this context, immaterial.