In an ideal world you're absolutely correct. That's the whole point of sovereignty -- where governments are in charge of things happening within their borders. Unfortunately, the US has a foreign policy where they routinely violate international law and meddle in the affairs of other countries. America is a quasi-empire. You can't do anything without their permission and support.
Gaddafi tried to create a pan-African currency backed by gold, thereby, becoming independent of white supremacist fiat system. Hillary Clinton, through the Clinton Foundation, NATO, and the French had him taken out. Many people don't have a problem with it because they've given into the 'evil dictator' narrative that the western media loves to use on puppet heads of states who go rogue (Hello Saddam).