BRICS, page-43

China's economy is dependent on exports for economic growth, imports for raw materials, they have a bleak demographic oulook with one of the most rapidly ageing populations in Asia which means their labour force has stop growing and they're losing their competitive advantage in simply transformed manufacturing and assembly.
The US has a much stronger demographics, access to a large pool of labour in central and south America. And can control the access to the most advanced technologies with much of new chip fab investment moving from Taiwan back to the US. These chips will give the US the competitive advantage in AI which can have a multiplier effect on all other sectors.

You're just repeating "the downfall of the US" without doing critical assessment of the relative economic strength of the US relative to China or Russia.