willingness to work hard is *not* a guarantee that a person will achieve financial prosperity. I have seen many people who are more than willing to work hard, but continue to live on the edge of poverty due to other bad choices. One young man, not yet 30 years old, has 7 children to support. He has no high school diploma and no special job skills. He has a learning disability and can barely read, but he'll bust his butt 14 hours a day without complaint. I doubt he'll ever achieve even a middle class lifestyle.
On the other hand, I am far lazier and less inclined to "work hard" than that young man. However, I did well in school (natural ability rather than hard work), went to college, and had the foresight to get a degree in a field that was easy (for me - natural ability not effort) and well paying. I work just 7.5 hours a day, get 50 paid days off per year, plus weekends, limited travel and very limited overtime. I earn substantially more than the average or median salary for where I live.
In the end, America is like Las Vegas - it's fantastic if you are lucky and crappy if you are not. You can win big, but you can also go bust and there's no safety net until you're at rock bottom.