The most direct impact would be an increase in costs because the American supply chain, which is currently almost completely dealt in dollars would need to fact

The most direct impact would be an increase in costs because the American supply chain, which is currently almost completely dealt in dollars would need to factor in currency risks, since, for example, they may have to start paying manufacturers in Yuan, and shippers in Euros. More indirect results would be things like making American companies less competitive than they are worldwide. For one thing, most American companies have little to no experience dealing with multi currency issues, while companies in other countries deal with these every day and do have experience. This will give those other countries and people a slight advantage against American competitors. Also, America gets a decent chunk of stuff for free or cheaper than it would otherwise, because countries are paying Americans goods and services in return for pieces of paper. Those benefits will gradually reduce and disappear.