Unfortunately there are not really any good options for high limit online blackjack if you're located in the USA. This is mainly due to the fact that all USA casinos have some sort of weekly withdrawal limits. There is clearly no point betting big if it's going to take a long time to get ytour winnings.
For example most US facing casinos have withdrawal limites of between $3,000 and $5,000 per week. Considering high limit players may want to bet more than this on a single hand there is not much point playing online at the moment.