In 1494 Portugal and Spain signed a deal to split the world between them. US and China didn't sign any deal but it's obvious.
Discussion
They both claim Taiwan though.
if you have a foot in enemy territory its a big advantage. Now it depends how far the US want to go to keep that. There's also Japan wich is another issue for China but Taiwan probably a bigger problem because they supply microchips to the US and that is a strategic resource.