I don't think the dollar fits the definition of a ponzi scheme.
"An investment swindle in which some early investors are paid off with money put up by later ones in order to encourage more and bigger risks" - Merriam Webster Dictionary
Isn't China doing this? Lending USA money which they will spend on chinese goods which will boost chineese economy? Both dollar and chineese economy are bigger and bigger buble. When it will finaly splash on full (and not like last time when US government printed trilion dollars and said crysis is over), it will be HUGE.