If the New immigrants were disillusioned by America, why didn't more of them return to the Old Country? Why did they congregate in slums?

Anyone in any other country would rather be here and dirt poor than in any other country in the world, we are not oppressed and you have a chance to rise if you are willing to work, it's a myth that people all hate America aSK the Mexicans why do they risk death to get here? but those that obtain visa's and then disappear they don't want to go back, even our worst situations is better than there best situation where they come from.