Hugh

Also, the US bases in Europe are not only there as a deterrent/protection for the Countries they are in, they are there to support power projection and minimise the "loss of strength gradient*". As we have seen in the current conflict, soldiers win battles, logistics win wars - by having permanent bases in Europe, many of the benefits that US military forces have operating in the United States are replicated overseas, and the loss of strength gradient starts from Europe, rather than the United States.

Also, the bases in Europe allow the USA to react quicker to hot-spots/issues in the Gulf/Mediterranean/Eastern Europe much faster/more consistently than if they had to ship everything over from 'Murica...

* the farther a military is operating from "home", the less power they can project to that area.