You are trying to prove too much with this example. American "meddling" has often been a good thing. Every country in the Western Hemisphere is now a democracy, thanks to our meddling.
The fact that we can't control every outcome is not a particularly persuasive argument against making any attempt to influence events in foreign countries.
That the countries of Latin America are democracies has nothing to do with US meddling. The Latin American countries became democracies in imitation of the US. When they got their independence they created Republics with constitutions modelled on that of the US.
Anyway, I fail to see why spreadin "democracy" is considered a good thing. Why should I care if my neighbors live in a democracy or a monarchy?