Yet millions still flock here every year in the hopes of a better life. Hrmm... I haven't heard of hordes of people looking to improve their lot going to the backwards Eastern European country from which you're probably posting.
I think you overestimate it by a tad. There's no flocking, just over a million immigrants a year. If you look at immigrants per year per head of population, the US comes in 31st. Just above most Western European countries, but way below Australia or Canada. Europe as a whole has a lot more immigrants per year than America does, and that includes Eastern Europe.
America hasn't been the promised land for a long time, and not that many people pick it out as the ideal place to live. It's just because American media doesn't cover any international news or events that Americans themselves don't realize this.