The US is rich for many reasons that have little to do with being well governed.
* The country was launched on most of a century of essentially "free" land grabs-- limited pushback from native civilizations. buying cheap from distressed foreign powers (Louisiana), the main wars of conquest being insignificant squabbles with Mexico over trifles.
* Said land was also compelling-- you weren't fighting the environment to extract value the way you would be in Siberia.
* After 1865, no significant nation-scale conflict on the territory itself to blow down existing investments.
* This created an opportunity for bulk immigration-- first with Homestead Act style programmes and then because the American economy was compelling enough to be a pull by itself. A high immigrant population has a unique "opt-in" demographics-- a situation that self-selects for entrepeneurialism.
None of this required wildly competent government. George Washington could have chosen to be a king, a religious caliph, or a protosocialist planning enthusiast, and the deck would have still held almost all the same cards.
The US is rich because it's well functioning.