Go watch Bill Clinton talk about illegal immigration and border security in the 90s. He'd be considered far right today. Read a book or newspaper from 50 years ago or 100 years ago and look at how much more freedom people had to build homes and businesses without a thousand licenses, permits, taxes and inspections.
There was a time in America where the notion of an income tax or of restrictions on running a business out of your home were considered far-left authoritarian and unconstitutional, but now we've all gotten used to a million regulations on how we use our private property, the government surveilling our communications and finances, government oversight and permission required for all activities.
Admittedly "left vs right" is hardly useful in contemporary politics, things are so multi-faceted and people's notions of what those terms mean is variable. But nonetheless, it's obvious that "the center" of American politics today is drastically far to the left from where it was previously.
In some sense, the 1960s counter-culture liberal progressives "won" and became the center and the establishment. A leftwing extremist in 1968 on issues of feminism, race, social welfare, tax policy, foreign policy, housing policy and probably others is a centrist today.
Environmental issues and unions are the only two areas I can think of where America has stayed the same or moved right since WWII.