The only thing that US bases in the EU are doing at the moment is contributing to the local economies. Expecting anything more is magical thinking.
Some US bases double as spy bases. For example in the UK, RAF Menwith Hill is an NSA spy base, and RAF Croughton is a CIA spy base. One bargaining chip Europe has is to oust these spy bases from their territory. This would obviously negatively impact the US' global intelligence efforts. In any case, I see little point in allowing a hostile nation have spy bases on one's land.