Houbi and HitBTC do not allow American customers. LUNA CLASSIC is on KuCoin, but not the new LUNA
KuCoin suggests the new Luna will be available for trading, but did not mention exactly how soon after the genesis. US exchanges that require KYC like OkCoin, Kraken, Coinbase, etc. would probably take longer to get listed as I assume there is a process for adding new tokens they have to go through.