One reason is that Tether is not a US company and does not itself operate in the USA. Submitting anything to a US court is a willingness to be subject to US rules and laws.
Tether is used by Americans, transacting with Americans on American soil, pegging itself to the American dollar, using American dollars as reserves, using the internet which is controlled by America, holding reserves in a banking system largely controlled by America...
Tether.to lists a US address and phone number. Their ip returns a cloudflare ip in California.
They are definitely subject to US law. Pretty sure the US could do things like have them arrested in their home countries, extradited, have their bank accounts seized, etc. I suspect the US could also seize all US dollars without the consent of any foreign nation as well, seems like a natural way to defend a currency. Hard to claim you're backed by US dollars in that case.
