You can't simply point to America, which is a totally disfunctional nation built upon greed and slave importing,

Africa and Brazil had far more slaves than the U.S. Where are both countries/continents today?

The U.S was a majority white country for most of its history. Other races had a choice to leave once the Emancipation Proclamation was passed and even an entirely new country in Africa was created for them [Liberia]. Yet how come Blacks, or Chinese, or Japanese never got the idea to build a boat and head back home, especially if you also believe it was their "labor" that made the country what it is today?

They practically didn't, without the White Man guiding them every step of the way. The only real mistake, was again, the 1960s Hart-Celler legislation which created a never ending stream of third world immigrants which has lead to the current demographic crisis. Otherwise, America was still the best place to live.