NO it couldn't. 4 nukes, Kyoto, Osaka, Tokyo and Nagoya and the majority of citizens are dust since the majority live in cities while 90% of the country is HIGHLY irradiated from the fallout. Japan's slightly smaller than California and Only about 33% of Japan's land area is inhabitable with arable land being 11.7% for food production because it has many mountainous areas and they're an ISLAND ARCAPELIGO which isn't the best option for sustaining a population, especially when that population is now irradiated. Hell the whole point of their invasions of China, Manchuria and Korea was because Japan had to compensate for their land of scarce of natural resources. Japan turned to those countries for oil, rubber and lumber in order to make up for the lack of resources in Japan. They still import most of its food from other countries due to not enough arable land and many raw materials needed for industry and energy.....They are HIGHLY dependent on allies.