They can attempt to pass the blame to the US Gov't, and maybe some individuals would be fooled, but larger investors wouldn't be and would see through their ruse and would both be upset and basically lose any faith they have in the system, making the value of Tether plummet. No one would touch Tether, making it worthless, since the big exchanges would then not let you exchange between <Coin> <-> Tether, and so even if they have some assets backing them up they would effectively be worthless as a company because of loss of trust.