Why do so many people want to come to the USA instead of making a better life in their own country?

I never understood why millions of people want to come to the USA. All it does it cause brain drain from your home countries keeping them economically poor forever. It’s bizarre to me that people will spend years and lots of money to live in the USA , but won’t spend a second trying to make life better in their own country.

Now guess what is happening in the USA now. People are growing increasingly anti immigrant especially if you come from a non European country. Largely in part due to many immigrants not assimilating or still speaking broken English.