Actually, I think it goes back to Reagan. Between FDR and Reagan, the big-government military-industrial neocon whatever you want to call them (it’s not dem vs gop, that’s for sure) had a pretty much uninterrupted chain of wins that eventually was going to turn us into a European social democracy with large, centralized government micromanaging as many aspects of citizen life as possible.
Reagan not only upset that progression, he empowered political opposition to that progression, which really didn’t exist in the Nixon/Ford/Rockefeller GOP. The result was an end to sixty years of Dem control in the House in 1994, an practical end to the same period of dominance in the Senate (although the Senate had flipped once or twice over that sixty years), and changed the discussion on the GOP side from “OK, how can we slow down this march to Europeanism” to “How can we reverse course and re-empower federalist thought.”
But, you’re right. We’re now like a bad marriage. The only way the US survives, in my view, is to get rid of the political control freaks in BOTH parties and return most governance to the states. Let California be California, and let Texas be Texas. As long as the government is trying to force California solutions on Texas, and vice versa, we’re screwed.