Immigrants prove that hard work really is still a predictor of success in the United States. However the system is definitely rigged.
I think you're saying that all hard-working immigrants succeed. But even I, as a non-American, have read stories of immigrants to the USA working 3 jobs and still struggling to pay the rent, let alone a mortgage.
Are they not working hard enough? If hard work alone was the predictor, why are there hard-working people struggling to pay for the most meagre of lifestyles?