Yes, USDT (also known as Tether) is legal in the United States. USDT is a type of cryptocurrency known as a stablecoin, which is designed to maintain a stable value by being pegged to a reserve of assets such as the US dollar. While the regulatory environment for cryptocurrencies in the United States is still evolving, USDT has not been banned or deemed illegal by any government agency.

However, it is important to note that the use of USDT, like any other cryptocurrency, carries certain risks. The value of USDT can fluctuate, and there have been concerns raised about the transparency of Tether's reserves and whether they are truly backed by sufficient assets. Additionally, there have been investigations and legal actions taken against Tether and its affiliated company Bitfinex in the past.

Overall, while USDT is legal in the United States, investors should exercise caution and conduct their own research before using it as a means of investment or transaction. It is always recommended to consult with a financial advisor or legal expert before engaging in any cryptocurrency-related activities.