That's part of the reason why in the minds of the majority Japanese, they want to nuclear bomb the shiit out of the US for a revenge one day. Just a fact, not saying they are doing it immediately. So US military is very very wary of Japanese military development. The other country the US is wary of is Germany. Both countries pose the greatest military threat to the US technically, and are of the least likely for the US to retreat their army from. China, on the other hand, is not a real threat. It doesn't have know-hows and is lack of political will to expand their power to the global stage.