The same mentality was used when the US kept bases in Japan, Germany and South Korea.
However when we get involved and then do not fortify the are things like Vietnam, Afghanistan and happen and it happened again in Iraq.
Iraq is not in the same category as Germany, Japan and S. Korea. Germany declared war against the US, Japan declared war against the US, and they both attacked the US. S. Korea was under US protectorship status N.Korea attacked the USA and a peace treaty still does not exist only a cease fire..
Iraq had a peace treaty with the US and the end result was that we should leave according to the Iraqi leaders. So we did....Not the first time the US vacated a place that they have controlled before, why is it such a big deal now?