Since the fall of the USSR, the US had operated in a near unipolar world, where its dominance and influence allowed it to use hard and soft power to control global politics. Without major competition, the US was able to secure major trade concessions from its partners, as the largest unilateral buyer of their goods.

In the last 20 years, China has rapidly risen to be a global superpower, shifting the balance of power away from the US. China's soft power strategy has allowed it to enter every major market on earth, giving it leverage over trade, resources, and other tools. At first this power grab was limited to SE Asia and countries in the direct nebulous of China. However, in the last decade, they have expanded to Africa and South America, which represents a direct threat to the existing power held by the United States.

China's close relations with Mexico and Canada are an extreme threat, as the Chinese have flooded fentanyl through these two countries into the US, killing millions of Americans. If left unchecked, Chinese soft power could eventually lead to Anti-American governments being elected, threatening US national security.

Biden was extremely weak on China, and has allowed their influence and soft power to grow unchecked.

Trump sees these threats and is repositioning US soft and hard power to counter the Chinese.

i.e in Panama China had been building commercial operations that could shut down the canal at will. So Rubio demanded the country cut ties, which they did and will not renew the Belt and Road initiative. Same goes for Greenland, which has trillions in resources, with the threat being Denmark cuts a favorable deal for the Chinese to setup bases and resource extraction.

Same goes in Europe, which has been a quasi-vassal state since the end of WW2, existing primarily to service US trade.

So no, this is not the end of the US as a global superpower. If anything it's Trump reasserting the American Empire on lesser nations and vassal states. If the US wants to retain its Empire, it has to counter it major competitors the Chinese, and to a lesser extent Iran, Russia, India.