I think prompters and circuit owners in the USA don't see a lot of up-side to hosting an F1 race. In most of the rest of the world, being an "F1 circuit" has a certain cachet, which affects its draw all year round. And I would imagine that lesser racing leagues are eager to race on the same circuit as "the big boys." Also, America, has its own major open wheel racing league, which focuses on the roundy-round circuits. When they do have occasion to race on a road circuit, they stoop to billing it a "Grand Prix," which doesn't help F1's cause in the least.
End result, in the USA, I would think the F1 weekend is pretty much the end of the investors' opportunity to recoup the cost of Bernie's race hosting fee, not to mention the extra million$ he will hit them up for for improvements and updates to the circuit and hospitality facilities.
And the fact that in those latter years they concentrated on such 'oddball' locations as Dallas and Vegas and Indy, and gave amiss to "real" road circuits at places such as Atlanta and Sebring and Laguna Seca, gives me to wonder if there isn't a widespread fear of taking up the serpent (i.e., Bernie).