While I agree that many American drivers aspire to IndyCar and NASCAR racing, anyone seriously involved in racing knows that F1 offers a bigger pay day than the Brickyard or Daytona could ever.
I think that the FIA really made sure that Americans had to leave America to earn their super license. Leaving home for a long shot when you can stay home and do 'pretty good' suddenly sounds better.
That said... the USA has more billionaires than anyone else, not a single one of them has a kid who wants to race in F1? Or even a family friend willing to put some kid onto the international stage? Doesn't even have to be like Stroll, Latifi, Mazepin or Norris. Perez has a ton of support from Carlos Slim.
Larry Ellison has had Oracle involved in international sports, why not F1? Mark Cuban loves sports and being on TV, how doesn't he have a stake in F1? Jay-Z built his fortune on Hip Hop culture, where Ferrari is definitely an important status symbol. Bringing a black American into F1, especially in the wake of Hamilton's success, would bring about as much 'street cred' as possible.