Who are we to tell the world what to do? We have rampant poverty, homeless children, no real healthcare or social safety net, and a drug problem that gets worse every day. Perhaps if we turned our attention to our own citizens and our own problems, we would then be able to help others outside our borders.
The US should stay out of other nations' politics because, besides it not being our business, we are not culturally aware enough to be into their politics. If another country wants its politics or political climate to change, it should be up to that country to work on it. Outsiders, and that includes the US, can only make a mess of things, because outsiders don't have a good understanding of the people of that country or how it could be governed effectively.
I don't think that this can have a cut and dry answer. There are obviously some times where the United States government should not get involved with the affairs of another country. There are also times where it would be unthinkable to not be involved, particularly in cases of gross human rights violations.
The United States of America for certain world events may need to perform things. The United States of America will do this for the security interest of itself and as well as other nations as well. This is for the protection of people that live here and we may need to continue.