I lived in the LA area for about 12 years and the San Francisco area for a few years, then moved to the Seattle area in 2000. I liked aspects of LA and loved San Francisco, but for tax and expense reasons moved out of California. I've been back to LA and SF multiple times since then.
All three of those areas have gotten significantly worse in the last 20 years, by what I see, in homelessness; crime; and trash, drug paraphernalia, and human waste on sidewalks and streets. Seattle is doing its best to follow San Francisco's lead.
I grew up near Detroit. Interestingly, Detroit seems to have hit bottom around 2010 after half a century of decline, and is on a little bit of an upswing. But it is still post apocalyptic. Americans (unless they live near places like Camden or maybe bad areas of Baltimore) have no idea.
A few Detroit stories.
When I lived in California, and my parents lived near Detroit, I would go back for Christmas. One one visit back in the late 1980's, a Northwest Airlines flight took off with incorrect flaps set, hit an overpass right after takeoff, crashed, and killed everyone. It didn't get far from Detroit Metro, but (according to the news cast I watched that night) before emergency crews got there, people were already looting the dead bodies.
Another Christmas vacation, I went back to visit with my girlfriend (now wife). She, I, and my parents went to Trapper's Alley in Greektown, which was very nice and fun, and safe because it is heavily patrolled all around its perimeter and interior. The People Mover (an elevated little rail system that makes a circuit around downtown Detroit, the result of one of the usual boondoggle projects that downtrodden cities do from time to time) had a station in Trapper's Alley. My wife wanted to go on the People Mover. My parents and I were nervous about that, as it went outside of Trapper's Alley. She (from LA) was incredulous and pushed for going. We did the little circuit. It was around 5:30 pm on a non-holiday weekday -- rush-hour time for most cities -- and as we rode around the heart of Detroit, the streets were mostly deserted. After we got home and were watching TV, the nightly news reported that the People Mover had been stopped and locked down later that night because someone had been shot on it, and the police wanted to keep the perpetrator from fleeing.
Another vacation to Detroit in early 2000's, we went to the Red Bull Air Races in Detroit, near the Renaissance Center. The air races were great! It was a summer weekend mid day with lots of people around. We took a little walk around the Ren Cen. The Ren Cen is a fancy, impressive building -- the headquarters of GM -- but within one block of the Ren Cen, there were already abandoned, burned-out rows of shops.
In 2012, I read a news article from one of the SF papers: "The Cheapest House in San Francisco". For half a $million, you could get a tiny, rickety shack surrounded by a chain-link fence. For laughs, I decided to see what $500k would buy in Detroit, and looked at various listings. $500k would buy a 5000 sq. ft. gorgeous mansion on large, grassy, treed grounds, all encircled by grand privacy hedges and wrought-iron walls. $250k would buy a 4000 sq. ft. mansion that looked like a castle, but only a large lot, no wrought-iron-enclosed compound. I went all the way down to $50k. $50k would buy a beautiful Tudor-style house, normal sized on a beautiful normal-sized treed lot.
However bad it might be for some cities these days, it can get a lot worse.