The US has a moral obligation to promote just governance in developing nations. They do not have the right to force this on nations who do not want it, but they have the right to promote it. Promoting something is usually harmless and there is no reason the US shouldn't promote just governance.
The United States is not required to police the world or to ensure that the entire world is safe for democracy. The idea that the US is capable of enforcing its dysfunctional ideals of democracy in every other nation in the world is laughable at best. The United States needs to focus on cleaning house at home and let the rest of the world learn to govern itself.