Unfortunately, it's always "defending US interests" which is the problem. Historically, US interests have been counter to strong local independent governments. The US has interests in low cost labor and natural resources. There are still a lot of people in the US gov. that are only incentivised to do the right thing if they get a major perk or kick back from doing it. I like to think that we're getting more progressive, and stepping away from the abhorrent shit our grandparents did to South/Central America, but then we get shit like trump withholding support from Ukraine unless they are willing to smear his political rivals. Then it becomes clear that there is still a very influential "old guard" in the government that prevents the US from actually defending the welfare of the many from the benefit of the few.