For weapons, alliances, food, knowing the way of the land. Basically, the native americans were used for the settlers surivival.
Hamilton was not a President of the US
Fred Korematsu argued that internment was unconstitutional mainly because internees did not receive due process.
In President Franklin D. Roosevelt’s EO 9066, residents from the West Coast who had Japanese ancestry were to be deemed as enemies. Fred Korematsu pointed out that internment violates his constitutional rights. He also pointed out that internment was an obvious type of racial discrimination.
One of many results of Japan's invasion of Korea in the 1500s was "gradual opening of Japanese culture to other influences," since this ended a period of relative Japanese isolation.