Once SEC are into you, there's no way out. Monero was one of the coin that was taken into consideration by the SEC and it's still not available to trade for US investors. Now it's time for ripple. Though US is not the largest market and exchanges are not the only way to trade crypto. But the US ban would have much more significant effect on Ripple than on Monero as the userbase of both the coins are different. Monero was already used avoiding popular exchange while Ripple is highly depended on centralized exchange.
I mean not all centralized exchange is following us regulations since they are in different states and different regulations to follow. I will wait for other popular exchange announce it so it may have big affect from US investors. I also heard that other investors from preparing their wallet to transfer it there than to sell it cheaper with today's price.