This is the kind of statement that only an American, and a very naive and ignorant of world matters at that, would ever make. US bases in Europe are no security at all.
They are a pest, relics of the cold war and unwelcome by the people of Western Europe. The US took advantage of the battered post-WWII European states and the (then real) threat of USSR, to promote NATO and establish army bases in Europe.
>I never hear discussions about Iran or Russia being a possible threat in Europe.
That's because a lot of Europeans actually follow world news and foreign policy and are not spoon fed the latest "enemies" by their media. Oh, and they travel to those "enemy" places and have been dealing with them, culturally, diplomatically and otherwise, for a millennium of so, instead of just hearing about them whenever their media gets its war mood on.
People in America can think that Iran or Russia are "a possible treat" because they rarely follow what's happening outside their hometown, and because all those ludicrous hollywood movies (I've seen tiny nations in Eastern Europe that their military couldn't hurt a fly even if they tried being portrayed as epicenters of plans to attack the US).
Discussing Iran as a (non terrorist) threat to Europe or the US is the kind of thing that only people needing advice from their Media to not conflate Chechnya and the Czech republic would consider.
>The thing that really gets on my nerves is that some politicians even want the US bases to be moved out from Europe. They simply don't understand the world in which they are living.
Oh, the irony.