Since the end of WW2 the U.S. has become, for better or worse, the world's stabilizing agent. Of course there are peaks and valleys - argue all you want about American intervention in the Middle East or South America - but broadly speaking world governments expect America to take care of business.

Huge swaths of modern society depend on the U.S. being a (relatively) honest broker and protector of "peace" - two notable examples of which, in fact, are Japan and Taiwan. The latter very arguably remains independent today thanks to American protection. If China chose to claim exclusive rights to the South China Sea tomorrow, it's unlikely that Japan or Taiwan or Vietnam or any coalition of coastal nations together - without American or pan-European support - could push back successfully.

All of this is shifting, of course, as nationalist movements gain momentum and confidence in America wanes but for the moment (and the immediate future), this is the world we live in.

https://en.wikipedia.org/wiki/List_of_active_Japan_Maritime_...

The "Air Self-Defense Force" has more combat jets that the UK's Royal Air Force, and almost as many as the mighty Israeli Air Force. The Japanese are just postured exclusively for national defense and territorial integrity....which many people don't realize includes the ability of executing credible counter-offensives to liberate lost territory. I would argue that until the past ~5-10 years or so, the Chinese stood no chance in a big fight out here in the First Island Chain. The qualitative AND quantitative differences between the Chinese and Japanese hardware were just that large.

This is only true of Japan, who as part of the WW2 reconstruction, agreed to draw up a pacifist constitution and receive protection from the US against threats in the Cold War era.

Asian leaders have "taken care of" plenty of business using US training, money and technology. Sukarno's regime in Indonesia killed 500k-1000k people alone in anti-communist purges in 1965-66. Back in those days, you could say the words "they'll nationalize the oil fields" and the US would come-a-runnin'.

https://web.archive.org/web/20180726044318/http://www.atimes...

So if economic activity is the metric that supposedly justifies US interest there, then the need to secure its vital maritime lines of communication is even more pronounced for China than for the US.

edit: plus freedom of nav demos

Conducting Naval operations in international waters with and at the request of our many allies in the region is something we've done since WWII.