What you fail to understand is that there is more,much more, to a nation than its economy. How would your people like it if millions of Japanese immigrated to the place where you came from and changed it into Japan v2.0? Oh wait, I’m sure your native country would never allow that.
If the Japanese immigrants improved the country, I would welcome them. Beside if you are not native American, you are an invader here as well, detested by the Native Americans.
The biggest blunder the Europeans who invaded north America, made was to import millions of slaves from Africa.
Nothing is free, and Americans are now paying the price for importing cheap low skilled labor from Africa.