Sure, that could work too (arming the locals). I don't think it would be as big of an undertaking as it would seem at first. After the third or forth oppressive govt is toppled, the rest will get in line or try and form together against us. Either way it leads to the death of more evil.
And no, America couldn't and shouldn't do this alone. We should create a new world organization that only liberal democracies with free markets can join. Then start kicking the bad guy ass. Starting with the easiest.
Yeah, it's not going to happen and there would be lots (and LOTS) of death in the short term and not all of those deaths would be bad guys. It would be hard and it's not even feasible today or in the immediate future....but assuming it goes well, we could enter a great new era for man.
How's that going in Iraq and Afghanistan? I simply don't see how one can justify robbing from people here to overthrow tons of governments overseas, and causing tons of collateral damage in the process. Do the ends of overthrowing murderous regimes justify the ends of robbing killing people? I say no.