How do you think the world would be if USA was not in every bodies nose.
The sad thing is, this has been on the cards since the end of the Cold War. Such is the nature of liberal democracy and free trade.
Its the immediacy of the current administration that is concerning.
I think the world would undoubtedly go through a period of adjustment, I'm not convinced that there would be world anarchy like some people think. If the US shut up shop tomorrow in terms of force projection:
The US economy would collapse
Russia would take the Baltic states
China would take the South China sea
Israel would stomp on Palestine
But on the whole I think the world would largely go on. Free trade stop wars by linking everyone's success to everyone elses. There isn't a country in the world that can afford to, or is able to go full isolationist.
China is happening and is going to happen big, nothing that the US will do is going to stop it, if they are lucky its might be slowing it down by a decade, but truthfully the world hasn't seen what China is going to be able to do. Everyone says were seeing the rise of the sleeping dragon. The dragon is still asleep, what we are seeing now is it just turning in its sleep.