https://en.wikipedia.org/wiki/Demographics_of_New_York_City

Population density in NYC ranges from 8.6k people/sqmi to 74k people/sqmi

https://en.wikipedia.org/wiki/San_Francisco_Bay_Area

San Fransisco manages 1.1k people/sqmi on average with a San Jose-San Francisco-Oakland, CA Combined Statistical Area density of 953 person/sqmi density.

The insane traffic in New York is easily avoidable if you're traveling to points on the subway line. If you're trying to take the Bay Shore ferry to Ocean Beach, you're going to have a bit of trouble getting from the LIRR to the port, because they never bothered to build a connecting route. But that's more a feature than a bug - Fire Island is made deliberately inaccessible as an enclave to the New York elites. Getting into and out of JFK and La Guardia airports is, similarly, nightmarish by design (or lack there of). Modern NYC city planners hate you for using any kind of public transit. But I can walk out my front door on 17th street Manhattan at 8am, amble over to the Amtrak, and be in DC by lunch. No other part of the country is like that.

Similarly, if you make it out to the Bronx or the north side of Manhattan (where they're having all the nasty flooding because nobody invested in proper build up / drainage up there) you can find some pretty cheap housing. Used to be you could find cheap housing all over Brooklyn and Staten Island too, but... it all got developed into "luxury" spaces with more sqft units for a smaller, wealthier group of people.

But to say SF has the same problems as NYC is wildly inaccurate. NYC simply could not exist under the conditions LA and SF have been developed. We're not just talking "bad traffic" but "not enough physical real estate to store that many cars". We're not just talking about homelessness but "physically not enough space for this many people".

NYC would look more like Connecticut or Rhode Island under the SF development model. Even suburban New Jersey manages higher density rates. At that scale, you're not "solving" homelessness. You're just defining it away by denying people the physical space to exist inside the city limits.

The meme presents dense development as a panacea, and it absolutely isn't. At the end of the day, more units at the same price point won't solve homelessness and more rail absent sufficient stations/operating hours can't serve the same public (as NYers are struggling to come to terms with). But the number of people who can and do live reasonably comfortably in NYC at a lower price point vastly outstrips the peers in California. And, as a consequence, the kind of problems NYC suffers from boil down to maintaining a heavily utilized urban environment rather than building one over the suburban sprawl that chokes off development at every turn.

Two totally different problems.