In all seriousness, they'd have to be at war with the US for that to happen I think. Clearly the US would outweigh them in power projection in space so yeah... if anyone happens to be up there when the bubble goes up, that very well could cross the fellow's mind.
Japan is more vulnerable in the event of a nuclear war. With a few thermonuclear weapons, it is possible to wipe out all of Japans major population centers. Japan is an island after all, they can do serious damage to the United States, but the United States is spread out over a much larger area. Most of Japan's land area is its Empire surrounding it, take out the Japanese home islands and its peripheral Empire will break apart, as they don't want to be in that Empire. If the United States were to lose a few cities, it would probably go on as a country or two. I think the former Confederates would not be happy with the Japanese nuking their cities either, and they'll want revenge, so in a limited nuclear exchange in the early 1960s, the United States wins by default although it takes much damage from this, the Japanese would be very unwise to get in a nuclear war with the United States, the US for its part would be unwise to start one as well, because even though it would win, it would receive so much damage as to be not worth the cost of its victory over Japan.
So I think the relations between the Japanese Empire would be "correct" that is they may be icy or strained, but both sides would be well aware that a full scale nuclear war would not be in their interests, that said the Japanese have no ideological reasons to have bad relations with the United States - they can't sell Toyotas, Hondas, Mitsubishis, and other Japanese products to the United States if they have bad relations with them and the US embargos their trade. The Japanese Car companies would be very unhappy with this situation as they want to sell cars. Purely in the interests of exporting their cars and products, the Japanese will want improved relations with the United States.
Japan is at a crossroads in the 1960s, they have to weigh what their Empire is costing them in lost export revenues to the United States versus what they can gain by continuing to plunder the subject people's under their control. The US President can say this, "You want to sell Japanese cars in the United States? Fine, but first you have to stop chopping heads and raping women in China, we'd like to see human rights more respected in the areas you control." Modernization, and economic growth of an export driven economy contradict having an Empire based on forced labor and economic exploitation, the areas they control are basically Third World, with not much wealth to be extracted excepting natural resources, or they can export cars and electronics with improved relations with the United States - their choice.
