You can't really keep $69,613,437,845.79 (at time of writing) in a bank. At that point, you are the bank. In the case of Tether, Deltec in the Bahamas. https://www.deltecbank.com/about-us/?locale=en

Tether themselves seem to be based in Taiwan: https://assets.ctfassets.net/vyse88cgwfbl/RPHIloRD3eE4J5QYNR...

Taiwan's extradition situation is .. informal. Because Taiwan does not officially exist. But there have been extraditions from Taiwan to the US.