In terms of Indonesia, it is not a done deal yet. Japan is already a lost cause for China-- absent a major, radical change in Japan's domestic political structuring. Korea, I guess, just wants to be on the safer side. But they seem to be less responsive to US pressure than Japan.
But, yes, the US is still quite powerful and influential in the Asia-Pacific.
In regards to the relationship between Japan-US-ROK,
Japan has is beginning to develop measures , and policies that may not be to the interest, anti-thetical, to US interests. I would like to cite two particular areas : 1) the closing of Futenma Air Base in Okinawa (which was in large response to local demands, and thus nationally mandated, the US conceded), 2) growing development ties with Russia; Japan and Russia are in the cusp of discussing about a joint-development of an oil pipeline to be built from Sakhalin to Hokkaido, Japan and Russia are also to conduct another set of naval operations and joint drills in Vladivostok between the Japanese Navy (JMSDF) and the Russian Navy. (against American protestation).
We see a growing awakening of Japan. And I welcome this.
US Officials: 2019 Closure of Futenma Air Station in Japan 'Fanciful Speculation'