Even if it were recognized, Sovereign Citizens would not be American citizens. Therefore they are illegal immigrants and would be deported (I dunno, to the ocean?) They have this whole thing about laws don't apply to them and shit. Welp if that's true what stops the US government from just abusing you? Or even just a gang of folks with guns shaking you down?

Sovereign cities are idiots and cheats who are trying to "game" the system by being petty criminals.