We don't have the manufacturing capabilities we had when WW I and WW II broke out for one thing, so the 'bring them all home' silliness isn't a good idea, and having a lot of forward bases is very much a great idea, and keeps the conflicts away from our shores. We learned isolationism is a joke and not a real possibility TWICE in the last century alone, so no need to make that mistake a third time, and with far less ability to respond to boot. You think the cost is high now, just wait until you have to rebuild entire industries from scratch while trying to stave off invasions and attacks while your trade routes are completely shut down by a dozen junk subs sent from some shtihole like NK.