> because the United States, so far, is still the most powerful country. ... But for how long?
What would be the competition to the US other than China (which is insular, nationalist to the extreme and protectionist to the extreme)?
If China is the only superpower competitor, then the structure you just described will continue to work perpetually as there is no alternative.
There is a common fantasy that the US is suddenly going to collapse, because 'all empires end.' It's nothing more than a fantasy because US wealth and power is derived from its domestic economic output, not from conquering foreigners or invading countries like Afghanistan (despite what the collapse-fantasy types would like to believe; the US already had the largest economy by 1890, long before the dollar became the global reserve standard). The US economy is built on its enormous scientific and R&D output, which is unrivaled in world history. That positioning of strength spans aerospace, spacetech, medtech, biotech, pharma, agriculture, software, mobile, semiconductors, intellectual property broadly, media & cultural export, finance & banking (Visa is worth $400b, Deutsche Bank is worth $16b; US banks are eating Europe right now, because of how weak their financial position is in contrast). The US is the world's #2 manufacturer by a large margin and is likely to regain ground on China from here forward (they will lose manufacturing share globally). The US has a position in energy that is unrivaled overall, including its oil and natural gas potential. The US has by far the strongest and most profitable airlines, which are now looking outward and beginning to buy into the rest of the world's weaker airlines.
The US still has 19 of the world's top 20 universities, and 40x of the top 50. That's one of its critical foundations supporting its economy in the post WW2 era. The rest of the world has nothing even remotely like it.
The US position is still expanding, not contracting. It has added an economy the size of Germany + France since the great recession. Simultaneously, China is gobbling up position / influence / economy / power in the other half of the world the US doesn't control.
There is no peer to the US in the 'West' and there is not going to be. Most of Europe has seen zero economic growth since 2006-2007, their stagnation is going to get worse rather than better. They will fall further behind (and their politics will get much worse as that happens). Japan (third largest economy) is going to see little to no economic growth for the next 20 years at least. So where's the competitor going to come from? It's not. The US will continue to grow more powerful, wealthier, and its economy will continue to out-grow Europe and its military capabilities will continue to expand far beyond what Europe is capable of.
China will be the sole competitor to the US in the 21st century and the two will split the world in half.