The Disparity Between Rich and Poor

Much has been made of the increasing disparity between the rich and poor in the United States, but I haven't really understood why it's happening or why something needs to be done about it. Thinking about this today, I wondered what factors have contributed to it. Here's what I came up with:

1.) Most immigrants arrive in the US penniless. This is the zero point of American poverty. As long as there are immigrants looking for better opportunities for themselves and their children, there will be poor people in the US.
2.) Upon arrival, first-generation Americans have to work very hard to accumulate wealth to the point of financial security, but because of their income level (and many times a higher-than-average number of children), they often have little or nothing to give their children to help them go to college or purchase cars or houses.
3.) The children are still better off than their parents. Because of a higher education level, a good work ethic learned from their parents and mastery of the English language, second-generation Americans can land better jobs than their parents did. They can earn more money and afford a higher standard of living. (Some may go to community colleges with government assistance and earn Associates' degrees or even better.)
4.) The children of second-generation Americans are completely assimilated. They've adopted American customs and dress, and don't speak with a noticeable accent. By working hard and making good financial and behavioral decisions, they can go to college and land salaried jobs they can retire from. They may even have a sizable inheritance they can pass down to the next generation.
5.) Once a family is able to pass family money from generation to generation, they can grow quite wealthy in just a few generations.

This is probably a typical scenario. Of course the kinds of jobs people have, the number of people a single income supports, their behavioral tendencies, and the social circles they are affiliated with can accelerate or break the cycle. The American custom of dual-incomes and fewer children has probably contributed much to the recent increase in the disparity between rich and poor. Remember the zero point stays the same: first generation Americans will almost always be poor, whether they are Irish immigrants in the 1900's or Mexicans in the 2000's. The only thing that changes is the how long a family has been in the US. My theory is that disparity between rich and poor comes not from racism or class warfare, but from the increased opportunities American people have created for their families over time.