THe USA should NOT be the world's police department, nor it's savior, its defender, its army.
American troops should NOT be deployed unilaterally to any foreign soil except in defense of the USA.
Problems in Darfur? Let the UN handle it. Iraq? Let the UN handle it.
There's no reason that the USA has to LIKE how a foreign government runs its country...Hell, if you're looking for a country to invade over human rights "violations," look at North Korea, China, Saudi Arabia, as well as many nations that the US considers "friendly nations."
The point at which the USA sends its troops should be set ridiculously high.
US corporation having problems with the local citizenry? Too fucking bad.
US Oil company getting fucked by the local government? Too fucking bad.
US Business interests are NOT something that should be protected by US troops.
The lives of foreign citizens in their own country should NOT be defended by US troops.
IMO, there's not a foreign nation whose citizenry is worth the life of a single American Soldier, Marine, Airman, of Sailor.
Defending the "homeland" is what the US Military should be used for. PERIOD.