When I arrived in the US, I sold USDT to get the US dollar
You have to define what the US dollar is, do you mean bank transfer? PayPal? Cash or another way?
If you have legal papers in the US, why not use a central platform?
My method is that I used the national currency to buy USDT through the P2P market.
How can you prove that these coins are legal "or from legal sources" if the sale is through P2P market?
Be careful not to deal with people in this forum. Many are scammers, you should ask before any transaction or use Bitcointalk escrow members --->
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I can do the highest level of KYC. If my USDT source is not legal, you can let the police find me at any time.