why did USA like interfereing other country's internal affairs?

I live in a country in which the US has a lot of influence. Not only they interfere in our inner affairs - we are also dependent on them in many fields. This might not give a moral right to meddle in our internal affairs, but sometimes, when someone cannot solve one's own problems, he should turn to the aid of some greater power. I'd rather this power would be the US, rather than Iran, for instance... The US are trying to help others. Sometimes they succeed, and sometimes they don't. I think that cooperation has a lot to do with the level of success... on the other hand, sometimes, a better understanding of the local population might have done most of the job for them.

well i'm from the uk so probably shouldn't be commenting on the us but i think that interferance is in order to gain power