The main way to buy cryptocurrencies such as Tethers, is through a so called “Exchange”. Exchange would let users buy Tethers using their credit card after “verifying their identity” by providing that exchange with is official ID card.
This process described as a security feature, is actually a trick from the governments forcing those exchanges to collect and share those personal information with them.
Once that done and because the ethereum blockchain used by Tether is public, those having your ID will be able to watch your wallet and see how you chose to use your funds.
However, there is a legal way to gain back your crypto privacy, it’s called a Tether / USDT Mixer.
Tether Mixer own different wallets (pools) and work in two steps:
They will use one of their liquidity pool to receive your USDT as well as other customers’ USDT.
Then they will use another of their liquidity pool to provide you with other USDT tokens (on a new wallet you created).
Therefore, the token you will receive on your new wallet after that mixing process will not be linked to your original blockchain.