40 years ago, but yes. If we hadn't stopped building 40 years ago the USA wouldn't be 1/5 nuclear, we'd be 5/5 nuclear.
Three Mile Island nuclear accident -> regulatory changes + drop in public confidence -> funding problems -> project delays and cancellations -> funding problems
or alternatively 40ish years ago was when the capital-holders really got their claws back into Western governments. nuclear being broadly a public endeavour, it didn’t really have a chance