a war involving both the Chinese and the Russians vs the United States is a world war, so yes, unrestricted submarine warfare is a definite. With luck such a war won't go nuclear.
However such a war would certainly involve the British, Japanese, Australian and South Korean Navies, probably that of Taiwan, and of course Canada and probably the Norwegians (which solves that SSN and SSK hulls needed that Calbear mentioned earlier).
It is entirely possible the Indian Navy would join in to help too and there is always the possibility the French, Italians and Germans help out.
The Eurasian powers (easier to than spelling out all four of them) also have lousy maritime geography, with a limited number of choke points they must pass to reach major sea lanes except those leading to Japan and Taiwan.
Even then merchant traffic can be rerouted further offshore, and thus using the Ryukyu Islands as a partial barrier.
I am not entirely uncertain that the Japanese Maritime Self Defense and Air Self Defense forces wouldn't be enough alone to handle anything the Russians could do, and with South Korean help handle the North Koreans too, leaving the Chinese to the USN and Taiwan, with Australian and Indian help
Russia is even more screwed as it has to get through the GIUK gap in the face of the USN, RN, and Norwegians and maybe the French too.
Iran has no blue water capability, and if it attacks shipping it will definitely bring in the Europeans and Japanese, as their primary fuel supply is the Middle East through the Persian Gulf.
As the tanker war showed in the 1980s, it is possible to damage super tankers but sinking them is pretty hard. As long as the USN doesn't stick its head into a meat grinder for the first few days it might even avoid losing a CVN.
The most effective weapon the Eurasians would have is mine warfare, which did very well in every single naval war which saw them used in the 20th Century. That could cause some problems, and certainly makes offensive action high risk for a while, but without other resources to defend them, minefields can eventually be swept.
I bet at most a couple of months of high intensity combat, and then its over
Also, a B52 or B1 with ALCM and Harpoons is a very deadly ship killer, and with GBUs is perfectly capable to taking out ships even in hardened pens and caves.
