I suspect we stayed in Europe in order to allow Germany an excuse to NOT have an effective military. Our expense to defend Europe and allow the European countries to slack off on defense is money well spent. Given that Germany is once again taking over Europe and through its EU government is beginning to threaten the Eastern EU countries that are balking at taking the Moslem invaders I think maybe we need to continue to preclude Germany developing an effective military, especially if Germany is in charge of a European Army, especially one filled by young men desperate such as is the Moslem population. That energy must be displaced or it will cause upheaval and revolution. The Arab countries are dumping their antsy young men onto Europe and relieving that pressure by venting it into Europe. China has the same problem and will have to deal with it by expansion and/or war. China is already dealing with it to some extent by virtual colonization of large portions of Africa.
Europe needs to contribute to its own defense but we should require them to pay more for our defense of Europe in assets and funds, not in replacing us with an essentially German large military.