One of the major reasons the US is rich is because the rest of the world has been using US dollars they receive to buy and sell oil instead of using them to buy US goods and services. It's like if I write a cheque to pay my landlord, who doesn't cash it, but uses it to pay his mortgage, and the bank uses it to pay their employees, and so on, without anyone ever cashing it. The wealth of the US comes at the rest of the worlds expense, for the most part, and they stablize and extend the system with their war machine.
With China now selling oil and natural gas in renminbi and Russia giving China unfettered access to their natural resources, there are going to be some pretty dramatic changes in store for the American people, and most of them don't appear to even have a clue.
They're going to need immigrants desperately, though, because they have a demographic imbalance that's going to leave them with too few young people to maintain things and care for all the retiring boomers.
If they were to close their doors and try to go it on their own, they would be so completely fucked that it's laughable to think about.
And the standard of living of the rest of the world would go up dramatically.