I really think you have this wrong. At the least, you need a better defense of your position. Assume for the moment that the number of USD in circulation is fi

I really think you have this wrong. At the least, you need a better defense of your position. Assume for the moment that the number of USD in circulation is fixed. (Presumably we agree that if the government prints or retires currency they can change the value of USD, so let's remove that as a factor). For the sake of argument let's say there are 10^13 USD at all times. Every year America produces some amount of real income. Let's just call that 1 A, measured relative to some fixed basket of goods. And let's say the government collects .2A in taxes. Now, you are saying that the value of USD is not constrained by this situation. Suppose that almost everyone switches to cryptocurrency and 1USD = 10^-16 A. Then at tax time Americans have to come up with 0.2A=2x10^15 USD which is 200x more than actually exist. So people will need more USD than they have and will have to bid the price up. Thus, given a fixed money supply and that the government doesn't literally instantly spend every tax dollar, there is a floor on the value of the USD proportional to total tax collection (and thus to the size of the economy being taxed).