The end of the 19th and beginning of the 20th centuries brought waves of a new kind of immigrant to America. The U.S. was suddenly peopled with millions of the poorest, most desperate, and most badly treated people the rest of the world had to offer. These immigrants brought with them little more than a powerful will to survive, and a wish to provide their children with better lives than they suffered. They wanted the American Dream for their kids. This attitude carried with it the strong social and work ethics that got the U.S. safely through the depression, WWII, Vietnam, and the Cold War.
Higher education is now common.
High School became, for the first time ever, a requirement of citizenship. Expectations ran high, and America became the best educated and advanced country in the world. Also, as their parents had hoped, life got much easier for the kids born in the 50's and sixties. Probably too easy. The boomers grew up in a world that was generally good to them.