These bases guard the interests of America.
No. That is not the first priority. For example, the main reason why the American bases exist in South Korea and Japan is to deter China and the DPRK from attacking these nations. Without the American military bases in South Korea, that country would have been over-run by the North Korean army many decades back.
Wrong! Of course these bases serve to protect these countries from China, but it is primarily a weakening of China and the increase in the number of supporters in the fight against him. Isn't it in the interests of the United States?