The real danger in the US is the ones FERC doesn't supervise. I'll actually politely contest your statement that most dams are federally regulated- most dams that are smaller are regulated at the state level (or at least, in my state they all are regulated that way) and those small ones are very common.

Of course, the small dams are in horrid shape and most haven't been adequately maintained in many years. They're not as catastrophic but we are still talking inundating thousands or tens of thousands of people sometimes depending on the location.

State agencies are much worse equipped to supervise such a vast field of infrastructure and so many don't, according to the correspondence and conversation I had with some engineers at my state's dam regulator. Those guys looked shell shocked and gave me like 12 hours of presentations and materials for free, saying I was the only owners representative in years to take any real interest in the dam on our property. Statewide. As in, they could not even reach live humans connected to any deeds or paperwork for most of their dams, and much of the rest was them getting stonewalled.

Silent and in the background, but terrifying.