You dont seem to understand Pax Romana. There were plenty of insurgencies and wars going on in the far off areas of the empire and beyond. The ones that put a hurt on Roman trade were dealt with and the ones that didnt affect Rome were ignored.

The trading, prosperous world (Europe, democratized Asia, South America to a certain extent) lives without fear of war or strife. Of course you could site Bosnia - but how important is that to the global trading community?

I believe we are living in a default Pax Americana - not an imposed order by the United States, but simply how the cards fell after WW2 and the cold war.

Because of American troops many important trading areas dont need to even bother spending money on a real army, and have become very prosperous indeed after ww2. Japan - Europe - South Korea.

So, to sound absolutely Roman, let the barbarians fight eachother as long as they want to as long as it doesnt affect Americas global interests.