If the US stops using paper money, the economy will collapse pretty much immediately (as would other countries' economies which peg their currencies to the US Dollar) and it would be forced to either use barter (I for one would not like having to bring chickens every time I want to buy something) or use a foreign currency such as the Ruble. Accepting currency isn't just a simple matter of wanting to use it, it's a matter of how it's used and what people will tend to start using as currency - There aren't universal ''Free Market'' laws which govern everything in the economy, it's much more complex than that. A good understanding of how the economy works requires at least a basic understanding of mass psychology, which you seem to lack.