Yes and no. Stake.us doesn't pay out real money for wins on their site. They award Stake Cash, a type of virtual currency which you can collect and redeem for gift cards, cryptocurrency, and other rewards. The speed depends on your chosen casino banking option.
Is Stake.us allowed in the US? Broadly speaking, yes, it absolutely is. In the vast majority of US states you can play slots, Stake Originals and other casino-style games legally.