So much American exceptionalism is just the Dollar exceptionalism.
Without the G7 piling up dollars, there is no American exceptionalism.
Dollar is the exception because the US is the exception (partially from luck, partially from its inherited geographical advantage), not the other way around.
The US has a lot of other things going for it. Rule of law, enterprise, most of the biggest companies in tech, entertainment and the like.
At some point the US will lose the Dollar, and it will turn out that US productivity is just like everyone else's.