There is no specific legislation on a federal level around crypto gambling. However, there is extensive state legislation around online gambling in general. For example, online gambling is completely legal in Connecticut, Delaware, Michigan, New Jersey, Pennsylvania, and West Virginia.
As mentioned in the section above, the US law doesn't ban or regulate crypto gambling on a federal level. FinCEN, a US government institution in charge of financial regulations, issued regulatory Guidance certain business models involving convertible virtual currencies.