Why is The USA shifting leftward

[Orser67]

The liberal New Deal, Keynesian consensus of the 1930s-1960s supported by the Greatest Generation and its predecessors was viewed by many as a failure after the Vietnam War, the stagflation of the 1970s, and (ironically) Watergate.

In reaction to these failures, the Reagan Revolution ushered in the "era of small government," and a belief in the value of the free market and the inefficiencies of government became widespread. Meanwhile, as the Greatest Generation died out, the more conservative Silent Generation and Baby Boomers became the dominant political actors in the country.

Generation X (especially the younger members of Gen X) and millennials didn't become disillusioned with government in the same way. They are also more concerned with the inequality and consumerism caused by the advent of free market principles, since the vast majority of this generation has to face the unalluring prospect of getting an entry-level job in a stagnant, free market economy, and many were a little alienated by the materialism of their parents. These generations are also less negative towards minorities, which makes them more open to redistributive programs which by their nature tend to help minorities more (to be clear, I am not saying that all conservatives are racist or vice versa).

Imo, the era of small government lasted from 1980 to 2008, when the country elected someone who could reasonably be called a liberal for the first time since 1964, and also elected a Democratic Congress. This didn't start in a "Liberal Revolution," but instead an era of intense polarization with a fairly liberal Democratic Party and a conservative Republican Party. Imo the only plausible argument that we haven't moved to the left would be that the 2006-2010 period (which saw the passage of the most liberal piece of legislation since the 1960s) was basically a fluke caused by a reaction to the unpopular Bush presidency.

[Orser67]

Name a single issue, other than gay marriage and perhaps drugs, where we are to the left of where we were a generation ago.  There aren't any!

Public opinion is, but public policy isn't.

Healthcare is a public policy that is to the left of where we were a generation ago. Medicaid is much larger and we have an individual mandate and subsidies. Medicaid also covers more benefits (due to Part D) and I assume (though I'm not certain) that the federal government has a greater role in K-12 education. Financial regulation is also perhaps "more liberal" than it was 20 years or 30 years ago (Glass-Steagall was repealed in 1999 but was pretty toothless even before that) after the passage of Dodd-Frank.