So why not let the entire population of Africa move to the United States? Borders are an antiquated concept according to you.
Wait, who is preventing the entire population of California from moving to Rhode island?
I'm not aware of any regulations that forbid anyone from moving to Rhode island from California, except for things like house arrest or other things requiring someone to stay in one place.
That said, CA and RI have similar quality of life, but Africa and North American probably do not. So CA/RI is not a good example.