Dks01 Your use of Japan is a perfect example of American imperialism, not motivation.
It was Japan that was imperialistic:
Japan occupied Taiwan as a colony from 1895 to 1945.
Japan seized and annexed Korea (1910), ruled it until 1945.
Japan invaded China (1937), Nanjing Massacre.
Nice guys, they were not.
The United States was downright [generous] to Japan after the war.
Especially when compared to the vindictive, vengeful treatment that the Soviet Union gave to what would become East Germany.
After the two atomic bombs were dropped—AFTER that, Stalin’s USSR finally declared war on Japan.
(Talk about coming in after the fact—).
It was fear of Soviet vengeance according to some historians, that was an additional final factor in Japan’s surrender.
IIRC, Stalin wanted the USSR to occupy part of Japan, and Douglas MacArthur said no way!
Japan did FAR FAR better under US administration than it would have under the Soviets.