Pax Americana will be around for a long time. No other power even comes close to matching our military and we are pulling away from most of the contenders at a rapid pace.
Can we continue to pour so much of our treasure into a world, where others will not lift a hand? The demographics of America have changed, we no longer have families of 5, 6 or 10 children. Can we afford to send off our best to fight for Europe, when they will not? (Kosovo, etc)