FIBA ball is actually more physical; No defensive 3 seconds, goaltending is legal etc.
While I agree that Team USA's underperformance is largely down to the rule variations, this also works the other way around. The underperformance of many EuroLeague guys in the NBA has the same explanation.
The EuroLeague is broadly considered the 2nd best basketball league in the world; but the last EuroLeague MVP born in the Americas was over 17 years ago; all the way back in 2006. If the ability gap between the NBA and EuroLeague is so great, why don't guys on lower NBA contracts simply jump over, dominate, earn more money and live in a better city? It's because they can't.