Of course, things can be nicer here in Europe on some of those axes, but I imagine most people starting startups in LA are not really choosing between LA and Copenhagen as serious alternatives.
I'll probably end up moving back to Vancouver, but honestly, somewhere in the Pacific Northwest (Portland, Seattle) is fine by me. I am interested in technology as an aide to build better, stronger cities, though; more of a social impact.
LA is doing things to improve; e.g., improving transit, building smaller communities (i.e., building smaller towns with grocery stores, walking areas/parks, places for entertainment, etc. in a smaller radius), cleaning the air, etc.
But all of this takes a lot of time and money, especially in the States/California. Money the state of California is reticent to invest it seems like. I'm happy that LA is doing things to improve, but it's going at a snail's pace. I'm a runner and have had numerous lung infections because I was so determined to run outside, as I think running should be done. Not even the beach towns are worth it.
Plus, it doesn't help that I don't like beach/"Industry" culture here (sunbathing, suntanning, plastic surgery, charlatans, etc.). This is my personal beef, so I understand there's a lot of varying taste/subjectivity involved.
Luckily, there are major NA cities ready to hire developers (not just tech companies or startups).