Trump can't physically follow through with his threat to Japan that he will dump 25 million Mexicans on the shore, though?
There are other ways that the US and Trump may be able to force Japan to be more multicultural like ourselves and be less xenophobic.
I suggest that the US put pressure on countries in the UN to all put pressure on Japan to change it's immigration policy to make it a lot easier for Mexicans and black people to move to Japan. Even put sanctions on Japan if necessary until they change this.
After WW2 we tried to make the country open to all, but the naturally racist Japs fought against this and maintained their racist ways sadly. They have no reservations about being caught out looking like xenophobic racists.
We need to all put pressure on Japan and force them to change their laws regarding naturalisation and also allow duel citizenship. Most conservatives agree with me, Japan has gotten away with being racist for far too long and we shouldn't put up with it.