I've been riding bikes to work every day in a few parts of Europe for about 10 years, including big cities traffic, suburbs and rural areas.

I've been doing the same in San Francisco for some month recently.

In Europe, everyone treat the bike as a vehicule, no question asked. Everyone knows the hand sign. People get doored, and the like but it's rare. You gotta be more careful in heavy traffic, but basically, when riding, it feels safe in most areas.
Cars will wait behind you when they can't pass super-safely-with-5-meter-distance-from-your-side almost every time.
Nearly everyone of them used a bike and knows how it is, at least, that's the feeling.

Now, fast forward to SF. I was surprised, to say the least.

If there is no bike lane, something like 90% of the cars simply do not give a single shit about bikes. That is, if you're on the rightmost part of the road, they will pass, no matter what (you can choose here: get even more right and risk being doored, the risk is rather high here. slow down to a near halt and go right [that's what I do]. go straight and hear the honk + generally get hit by the rear view mirror.)

Knowing that you can avoid streets without a bike lane, and when forced, take the full lane (you'll hear the honk but you'll live).

Here's one that happened to me recently: some streets in SF have a tram lane and a car lane. No bike lane. car pushed me on the tram lane thinking 'thats where cyclists go'. Tram was coming behind of course. Got to feel the friction of both car and tram. No injuries. Unfortunately I don't have a good alternative route.

Here's another thing that happens everyday:

Car park in the bike lane, so you gotta pass it. Look behind you, car is coming, so you slow down, and let them pass (they will never let you pass). If there is a continuous flow of cars, and it happens, none will let you pass. Most cyclists just pass and assume the driver will slow down (and get angry but hey, you gotta pass some day). Personally, I just wait as long as it takes or walk it on the side walk if its more than a minute.

Pedestrians are no better. They don't cross at red if cars are coming. But they do for bikes. Why the hell? I understand crossing at red when it's safe, don't get me wrong, but don't cross in front of bikes that's extremely dumb.

Cyclists are no better either. 50% (?) ignore the signs and traffic entirely.
That being said I noticed that in some parts of the city this is actually safer to cross at the red light while cars are waiting, than waiting with the cars (in line or slightly in front, although I always go slightly i front to be sure they see me). Sad but true. If you start with the cars, they wont let you start first and thus you may get hit if the bike lane is not wide enough or simply not there.
Even if there is a bike lane, its gone when there's a crossing and drivers naturally push you on the right side for some reason. I still stop at all traffic lights but this is disturbing me a lot lately. Whats the point of respecting the red light in all situations in the US, being killed? and I bet that's why so many ignore them.

Finally, after a few month I personally got "right turned", and broke some bones, hence my super-safe behavior assuming the driver is going to be doing the wrong thing in every situation. Before I would expect that some situations were safe, such as the right turn if you're in front of the cars. But no. They just turn into you even thus they've seen you, because, you're a bike, you'll probably brake in time, plus you should be on the sidewalk, etc.
So yeah, I never cross a street without slowing down a lot if a car is less than 10 meters behind me (and obviously if its next to me or slightly ahead, even thus I'm on a bike lane, although they're supposed to switch lane)

As a last anecdotal story of this very long post, I was also surprised by rainy days. About, let's say, 15% of the cars take the opportunity to splash you when they can. Seriously. My last rainy day in SF, that happened 3 times over my 20min ride back home. The last one the guy stopped and laughed. I was 100% soaked. It means to me that a high enough number of drivers absolutely hate cyclists with passion. WTF is wrong with people?