Memes

It really isn't that right-wing, especially economically, but there's a lot of factors that make it seem that way. First is that it did go through a large, neoliberal shift int he 80s during the Regan years. When the economy crashed in the early 90s, the Democrats decided that, instead of returning to their New Deal roots, they would also run on neoliberal policies. The Republicans moved further right because of that, especially on social issues, and then the Rachet Effect described in the meme really started to ramp up.

Couple this with a lot of political illiteracy among the public in general, and you get a lot of people who actually don't know what they believe and default to partisanship. If you poll people if they support gun control, you will get a very negative response, but if you break gun control into individual measures (longer waiting periods, mandatory background checks, magazine capacity limits, etc.) you get much more support. It's the same on almost every issue; people don't support a, "big government takeover," of the healthcare system, but they broadly support Medicare for all. There's a somewhat famous picture of a guy holding a sign that says something like, "Get Your Government Hands Off My Social Security," that I think sums up this ignorance pretty well.

This attitude isn't limited to the right, either. If you asked a Democrat "Who deregulated Wall Street?" they'd probably tell you Regan, Bush, or the other Bush. In actuality, the most significant deregulation, which lead directly to the 2008 financial collapse, was Clinton's repeal of Glass-Steagal. Liberals think that Obama made a significant progress on regulated Wall Street, but what he put in place was nothing compared to the deregulation that proceeded it.

Citizens United and the rise of mega donors also plays a pretty significant role in moving the parties away from policies that the general population want and towards the goals of a few oligarchs, but this reply is already way too long, so TL;DR: the country got pretty right-wing under Regan, both parties became more right-wing as a result, the population has become much more left-leaning since income inequality/cost of living went way up, but the parties are still both right-wing and most people are too ignorant to understand that.