Regarding commuting via bicycle: it's not necessarily a problem with traffic, as more with weather. Also it's wrong to compare a single city, Amsterdam, with a bunch of American cities because of drastically different weather patterns in those cities.
Amsterdam has average temps (in F) from the mid 30's to the mid 60's[0]. That's prime bike weather. That's pretty much in line with San Francisco, which is a good city for biking. Even Manhattan and Brooklyn have reasonably overall pleasant weather for biking.
But compare SF to somewhere like Washington, DC, or Austin, TX. For 3-4 months of the year, DC feels like a swamp. Same with Austin. It's much more preferable to use public transit or drive than bike in that weather.
Amsterdam has average temps (in F) from the mid 30's to the mid 60's[0]. That's prime bike weather. That's pretty much in line with San Francisco, which is a good city for biking. Even Manhattan and Brooklyn have reasonably overall pleasant weather for biking.
But compare SF to somewhere like Washington, DC, or Austin, TX. For 3-4 months of the year, DC feels like a swamp. Same with Austin. It's much more preferable to use public transit or drive than bike in that weather.
[0]http://www.holiday-weather.com/amsterdam/averages/