Both epidemic and screwtape make good points. True: The US was sheltered from global competition for 50 years after WWII. True: The rest of the world is now catching up. But at the same time, US domestic policies have increasingly favored the wealthy-- who don't work-- over the poor and middle class who do.
And no, it has never been the case that "anyone who works hard can get rich". My working class students think this way, and I ask them why their parents and grandparents did not get rich. The easy answer is that life happened, and you don't get rich driving a bus, teaching kindergarden or delivering mail. You most definitely don't get rich caring for your children or elderly parents. Basically, normal families can't get rich! But you should not have to be rich to have a decent life with a level of stability.
Most people in Europe, Latin America, Asia, etc, realize this and try to have government policies, including higher taxes, so everyone can meet their basic needs,and access good education and have health care regardless of income. We in the US are still not sure whether everyone deserves these things. We would rather have access to a gun and low tax rates (so it seems).
Productivity is the US is at record high levels. But the increased value has not gone to the workers who produced it in the form of increased wages or benefits. The increased value has gone into higher profits and higher salaries and more benefits to those at the very top.
Deregulation of industries, cutting taxes, and allowing for rich people to escape taxes, has led to defunding the education and social services that allow poor and middle class people --those without rich ancestors and big inheritances-- to have a chance at upward mobility.
When people complain about increased work loads, decreased hours and unpaid furloughs, enforced overtime, no raises, cuts in benefits, safety net full of holes, crappy infrastructure, they are told to be grateful to have a job at all. Because you could get laid off, and then where will you be?
And we are encouraged to blame those at the bottom, the least powerful for the situation (like illegal immigrants who do the crappiest jobs for the least money) as if the policies from the top have nothing to do with it. Unions and political organizing can help, but only if people know what the problems really are.
Not to sound too Marxist, but there it is.