Don't worry, the same thing happened to Russia, US submarines are also in close proximity from all important cities in Russia. This is called Sampson Option.
And also close to China mainland too.
By international law, only 12 miles from the land belongs to one country, so putting submarines say 13 miles from US land will be fine, likewise putting US submarines around 13 miles from Russia's mainland and China's mainland is fine too according to international law.
What do you think prevent war so far? Complete annihilation of each other ... even Israel put its submarines near Russia's mainland and Iran's mainland. No one knows where the submarines are even the President doesn't know where they are. This is to make sure a blowing and hard counter attack by submarines enough to devastate the whole Russia or China. Their commands are only one: "making sure a fatal counterattack in case of sudden attack on the mainland"
So .... don't worry .. but if one player is crazy enough, the world war will break out and it is a complete disaster for all others....
Gimel Israel