In the inter-war years, the UK was no longer concerned with Germany, but, due to the Great Depression, was also too damn broke to go on international adventures. The same situation played out in the US.
The only reason the two powers are now aligned, is because the United States started seeing communism, as opposed to European colonialism[1] as its biggest threat.
The moral of this story is that superpowers can have friendly relationships when they have a common enemy, or no conflicting goals.
An obvious question, here is - what are the conflicting goals of China, and the United States? The answer is - influence among China's neighbours. If the US was not interested in maintaining it, there would be no conflict.
[1] In the 19th century, European colonialism was a threat to American colonialism. In the 20th century, the American empire has resisted de-colonization a lot better then European powers did.
The optics of it were anti-colonial. The implementation of it was absolutely colonial. This is one of the many baffling contradictions of America.
Central and South American states were only allowed to be independent of European rule. They were, and continue to, be client states of Washington. When they forget this, they get regime-changed.
America's 19th and 20th century adventures in Hawaii, the Philippines, Samoa, Cuba, Puerto Rico, the annexation of Mexico's territories, and deportation and repression of native Americans were all colonial power grabs - and all performed under the aegis of the Monroe Doctrine.
This is the fundamental difference between the British Empire of yesteryear, and the American empire of today. The British public was never confused as to whether or not it was at the head of a globe-spanning empire.