2. Middle class and rich people rarely immigrate. It's the poor that do. Did you know that the reason the Titanic was built was to en-masse ship poor people to the US? The first class bit was mostly window dressing. The money was to be made by cramming poor people in below decks. In colonial times, America was populated mostly by people escaping prosecution, indentured servants, sons who weren't first born and were not going to inherit anything, teens whose parents could not support them, etc. The Chinese and Japanese people came to escape poverty.
Furthermore, South America was and is rich in resources, but it remains poor. Nothing like the US happened there.