

Its duty?!
The US has no mandate to meddle in international affairs, any more than a bully in grade school has a duty to stop smaller bullies from picking on their own victims.
The US has never been an international savior, it’s the only country in the world to have dropped nuclear bombs on civilians.
What other things, specifically?
Imo fascism is a natural consequence of hate and apathy. Introspection by individuals and willingness to change are how you overcome those issues. Governments can’t force people to empathize but perhaps better education and less superstition can help.