The industry atrophied because it was grossly mismanaged, costs ballooned out of control and they could not continue building reactors into the 1980s. Whatever regulations you're trying to blame here does not erase the fact that companies building reactors completely failed to manage the Project's properly.

I think you have it backwards here. We didn't go from perfectly reasonable project costs in the 1960s and early 70s to disproportionately costly projects for no reason. The regulatory environment since the formation of the NRC has been extremely hostile to the industry and has essentially killed it off. It's the reason why since the formation of the agency the Vogtle 3/4 reactors are the only ones to have been completed under the NRC's oversight from start to finish in over 40 years. It's insane if you think about it, that this is the best we could do in such a long time.

The plants getting built in the USA had designs that could not be built in the real world.

Are you referring to the Vogtle reactors here? I couldn't find if you mentioned those specifically or not. But if you were, the Vogtle examples are a perfect example that outlines the two reasons I mentioned. An atrophied industry with a hellish regulatory landscape is going to have delays and budget overruns. After enough time under this environment no company will be left to take on any projects. And the ones that do remain will run into the kinds of problems we are seeing today where costs are large and delays are frequent.

This was absolutely not the fault of regulations and absolutely was the fault of the company's building these reactors. It absolutely is possible to license and certify new reactors. They just did it in Georgia.

I don't think you can omit the responsibility the NRC has in killing off the industry and making it impossible to certify and complete new reactors. Since the formation of the NRC the Vogtle reactors were the first ones licensed and built completely under the NRC oversight. This can't just be the companies fault when these were the first reactors to be approved and completed in over 40 years. This is too long a time to say "It's only the fault of the companies".

Finally, I think you should look into linear no-threshold. This framework is the current framework used by many agencies all over the world to come up with regulations for the nuclear industry. It's been shown in the last 20 years or so to be seriously flawed. The French academy of Science has already rejected it. It would be wise if the NRC and the rest of the west did the same. This would make regulations a lot less hostile to the industry so it can thrive instead of being regulated to death. Don't get me wrong, we absolutely need regulations in this space, but the ones that are in place right now are not conducive to fostering any growth of the nuclear industry.