I'm fairly certain that the US was large and spread out well before cars were invented.

On a large scale, yes. But urban sprawl is directly caused by the automobile.

The design of US cities is just godawful from any perspective (environmental, social, business efficiency, crime rates, ghettoization, etc), compared to those in Europe. I'm fairly certain that Manhattan and San Francisco are so vibrant and livable largely because they're constrained by geographical barriers.

It's a bit of a stretch to refer to most large European cities being "designed", at least recently, isn't it?

The urban cores are very old, but many of them are surprisingly small, with the bulk of the city dating to the past 100-150 years. Copenhagen's old center, for example, was less than 10km across (confined within city walls until the 1850s), so nearly the entire city was laid out according to 19th- and 20th-century urban plans (the 20th-century one was http://en.wikipedia.org/wiki/Finger_Plan).

The city where it's architecturally most visible is probably Barcelona, where you can see the medieval core's winding streets, and then a massive expanse of centrally planned regular squares outside of that: http://en.wikipedia.org/wiki/File:Eixample_aire.jpg

Thanks! :)

I thought it was people fleeing the inner city for the suburbs that caused sprawl.

It sucks, but so do the cramped cities like SF and Manhattan. You can never get a moment's peace and contemplation, and they're even more crassly commercial than your average strip mall.

Sure, it was always large, but suburban sprawl was not always a thing. As cars became ubiquitous, things got more spread out, and designed with cars as the assumed primary mode of transportation. This was not necessarily a good idea.

Or it could be that not everyone wants to live in a crowded city in a small apartment. Some people prefer to be a bit more spread out, perhaps near nature.