What will America do when it's not the only superpower?

Not really. It would be what China is today, actually. Which aint bad.

I’ll bet we still have the stationary.

It depends on how you measure China.

For example, keep in mind most people in China are peasants. In fact, IIRC the majority still live in homes without electricity.

Sometime we get too wrapped up in the big picture and miss the little picture.

China may be a “superpower” in ways that Japan, Iran, and the UK aren’t, but I’d rather live in any of them over the PRC.

Hold that thought until the USD loses its reserve currency status and US external debt starts to be non-USD denominated. 'Tis a whole different kettle of fish.