Good point...US troops are still protecting Germany and France - from WHAT? Pres Eisenhower was right, "Beware of the military complex".
Mainly for political reasons we devote 40% of our fed budget to the war machine - much of which, btw, has outdated systems given how todays wars are/will be fought. It stands to reason if we can afford this, we surely can afford to take care of our OWN at home.
When a country spends 40% of their budget on the war machine they have to look for wars to use them - and we do, again and again.