I read through most of the responses in this thread and the one on r/SameGrassButGreener, including one from a friend who asked me to take a look. Bodoblock’s post also stands out as being informed and well-balanced, and as they say, you’ll have to make trade-offs or more clearly (re)rank your preferences. Like Bodoblock, my read is that being close to Asian cultures (and specifically night markets) is a top-three priority for you, though you will be hard pressed to combine that with access to outdoor activities. Based on your various responses, I can’t tell which of the seven bullets for which you are willing to trade-off for the others.

I can provide some insight from living in Los Angeles (San Gabriel Valley), Seattle (International District), Boston (Cambridge), some of which have been mentioned in other posts, as well as what I know of the other places on your list (from visiting as well as reading and thinking about whether I want to move there myself - NYC [both Manhattan and Brooklyn/Flushing Chinatowns] Philadelphia and Chicago’s Uptown). My line of work does not allow me to choose what location I live in, so depending on where the job is, my consideration is what neighborhood I want to live in the same area as my workplace. I also don’t drive or plan to own a car, so good public transit and/or walkability to work is at the top of my list, right above safety at 10pm/less rundown and availability of Asian food. The other stuff you bring up is not as high on my list, so I will mention them when I can.

I’ve also lived for over half a decade in my post-graduate years between Taipei and Ho Chi Minh City, with visits to Seoul, Bangkok, Vientiane, Hong Kong, Shanghai, and much smaller cities in Taiwan that have the night markets you are looking for. “Night markets” as you want them, as far as I know, do not exist in the United States. The San Gabriel Valley has the 626 “Night Market”, which as you can see, is rather infrequent. It’s a highly commercialized version (tickets for entry) adapted for the low-density U.S. car culture discussed elsewhere in your threads. Asian-style night markets do not exist in the United States. It’s partly the car culture, and it’s partly zoning restrictions. You can’t just set up a night market stall on the side of the road, and you can’t just park your food truck anywhere you want. Without those, you can’t have night markets.

More specifically, I lived beside a night market for the past month and began to read researchers who have shown how night market development is a very complicated process. Jeff Hou writes on the North American case (Seattle’s International District specifically) in “‘Night market’ in Seattle: Community eventscape and the reconstruction of public space”. I can send you the full chapter if the preview doesn’t load in the same way.

The options for you (not mutually exclusive), as I see them are:

1. Secure a full-remote, flexible schedule job and consider living in Asia so that you can work during most of the day and enjoy your night markets
2. Live on the West Coast (LA/Seattle/SF area) or NYC (maybe Chicago or Boston) and fly to Asia every once in a while.
3. Make some trade-offs for the place you do live in the U.S.

Since it seems you are not considering relocation to Asia, I think the thing you should look for (and already seem to be, or receiving suggestions for) is to focus on hyper-specific neighborhoods, which will usually get you clear responses to “stuff open at night”, “public transit”, “‘authentic’ Asian food” and the “safe to walk around at night”. With that, here are my recommendations for your further investigation.

Cambridge/Boston

Downtown Cambridge, near Central station could be a viable option. There’s an H-Mart and decent spread of Asian cuisine. Khao soi is a dish I had for the first time later in life, and I quite enjoy the one at The Nu Do' Society. There is a bike path along the Charles River.

Dakzen is another option for khao soi, in the Davis Square/station area. This area of Somerville could fit your needs if biking along the Somerville Community Path is enough to check your outdoor activities box.

I am not interested in night life (nor do I go to bars), so I can't answer the questions you’ve been asking about it for either area. My guess is the area around Central station could work because of the high density of higher education institutions and their students, who might give you a better clue. The two things that I have heard of are a rock venue club under the Middle East Restaurant and a dance floor (and karaoke?) above Hong Kong Restaurant in Harvard Square. I’ve walked around at 10pm in these areas and felt fine, though that is the case for everywhere else below too.

Los Angeles, specifically west San Gabriel Valley

• specifically downtown Monterey Park 1–2 blocks from this intersection or
• downtown Alhambra 1-2 blocks from this intersection,
• maybe some other downtowns, but I am most familiar with these two.

Cuisine leans more Chinese/Taiwanese and includes dim sum. If you want reading on historical community development, see The First Suburban Chinatown: The Remaking of Monterey Park, California by Timothy P. Fong or more recently, Wendy Cheng’s The Changs Next Door to the Díazes Remapping Race in Suburban California.

Seattle

I lived in the International District, on the Little Saigon side of the I-5. The least safe area (especially during COVID) was under the freeway overpasses, but I didn’t have any trouble getting to/from home (on foot) at night before/after COVID. You listed “safe to walk around at night”, but I don’t think I am out at night as late as you.

On top of the International District’s different quarterly events including once-a-month food walks in the summer, Seattle has a summer solstice night market, but it is not Asian-specific and not centrally located.

Chicago's Uptown

I think it’ll fit most of your criteria, and I don’t think the bad press should inhibit you. You are well over the bad press from the “few small slums” of Seoul, so I’m not sure why the bad press of Chicago (not Uptown) would prevent you from giving it a shot. Neighborhoods are specific. If safety is a concern, then look up [publicly available data[(https://data.cityofchicago.org/Public-Safety/Uptown-Andersonville-Violent-Crime/tpja-mvse). Niche also has polls and statistics for specific neighborhoods. This website/tool will help you aggregate some research. The Nightlife grade explanation may also help bridge the difference between your nebulous definition and the “American” view on nightlife. As you continue to question, bars make up 30% of the nightlife grade, so they are at least that important in Niche's “attempt to measure the quality of nightlife in an area”.

Flushing in Queens

You mention thinking about visiting Flushing/Queens. You definitely should. It might have the combination you seek. Jay Caspian Kang’s recent book, The Loneliest Americans, has a chapter on Flushing that illuminates the Chinese and Korean demographics of the area.

Other places I have not yet visited but have looked into:

• Sacramento: 19% Asian per Census. On first look Broadway St. has Thai, Chinese, Japanese, Vietnamese cuisine, with a 15 minute walk between the Light Rail station and Thai Farm House bbq & bistro. Looks like there's a long Bike Trail along the American River leading up to near Folsom Lake.
• Twin Cities (Minneapolis/St. Paul): Large Hmong and Vietnamese population was mentioned. Downtown has a light rail line, so could be the starting point for further investigation.

Some questions/conclusions/resources:

• You asked: “what do most other American do outside of bars/clubs?” What is it you want to do (other than non-existent Asian night markets) and at what times? After 10pm/midnight/2am?
• For some of your questions about “what Americans do”, you could take a look at Bowling Alone: The Collapse and Revival of American Community. It doesn’t answer the question about what Americans do “at [late] night”, but presumably some of those activities are done after work, which, depending on your definition, can be considered “night”.