The US, like every geopolitical entity to ever exist, has produced global public goods (i.e. international security, defeating the Nazis, etc) and global public bads (greenhouse gases, failed interference in other countries, etc).
I would like to posit something very simple: the greatest public good the United States has ever produced is the option to leave where you are and emigrate to the United States. If a country and its leadership is failing, non-trivial fractions of their population had the viable option to pack their bags and walk out the door. Perhaps unfairly, this is doubly true for their best, brightest, and most endowed with resources, making the threat all the more salient. It’s voting with your feet i.e. Tiebout effects writ large.
If you are a failing nation, your options become to watch your population dissipate or put up a wall blocking exit. Either that or, you know, actively take steps to improve your country so that fewer people wish to leave their home and start over elsewhere. The ramifications of stifled immigraion to the United States will be felt for decades, and not just in the United States in the form of an enervated economy and betrayal of our core civic values, but globally in weakended constraints on every failing regime.
Economist Writing Every Day 