The original pre-cuts STS program would have really been something. But once Apollo "won the race" there was no more governmental will in the US to do space research and infrastructure in a more than token way.

The Falcon 9 isn't actually throttling that deep either, it's just lighting a smaller number of engines for the same effect. 3/9 for the boostback, 1/9 for the final landing. But of course running a large number of engines at once presents its own set of problems, as seen in the N1. Falcon Heavy getting 27 rocket engines to work together is another of those legitimately impressive things you do have to hand it to the workers at SpaceX for.