Thanks for all the info, fellow CC-ers! Lots to digest here. What is certain is that unilaterally becoming the "policeman of the world" is a huge headache that ordinary American citizens never wanted for their nation.
For the record, as a general rule, I support the right of people everywhere to self determine their governance. Most simply don't have the fortitude to do so, however, and it's not our job to do it for them. Unless specifically asked for aid, the USA should just keep its nose out of other nations business unless it directly impacts our own safety.