Yes, this is pretty much how it played out in other countries as well. Involuntary commitment has a very nasty history associated with it - rampant abuse, suicides, forced sterilization and lobotomies, untested electroshock therapy, unethical medical experimentation, pretty much every horrible human rights abuse that you can think of, up to and including genocide. By the 70s it had become socially untenable, and by the end of the century most countries had shuttered their publicly-run mental health institutions.

What is fascinating to me is that you can plainly see this evolution of thought play out in books, music and film. The portrayal of involuntary commitment slowly shifts from something that is normalized and somewhat necessary for society at the beginning of the 20th century, to something that is unabashedly evil by the end of it.

And it's so obvious as to why/how in retrospect

Everyone knows sending an innocent person to prison is really bad. But if you throw "they're not well..." in front of it and you have all the green lights you need.

>> Lanterman-Prentis-Short Act of '67 capped the length of involuntary commitment half a decade before the SCOTUS decisions

Mostly agree with your argument and I'm a Reagan fanboy, but Reagan did put his signature on that law. It was a bi-partisan bill (Lanterman was a Republican, Petris and Short were Democrats), and it passed with veto-proof near unanimous majorities, but he put his name on it.