Just come back from a week on the Easy Coast looking at 9 different unis in 5 days! My head is spinning!!
The main difference seemed to me, as mummytime said, is that the degrees tend to be liberal arts ones and, depending on the institution, certain subjects are compulsory in the first year, regardless of what you intend to major in. Most seemed to require students to do an essay writing course, some required maths and some a foreign language. The language could be studied from scratch, but I don't think you got as many credits for that. Engineering was always said to be treated completely differently (I don't know how!), and geography never got a mention. In essence, if your DS knew he wanted to focus entirely on physics, or history, for example he might be better off in the UK.
Most places offered 4 years living on campus, and most students seemed to do this, which I think is different from the UK. There also seemed to be a lot of jobs offered by the colleges for the students.
Some offered some sort of programme in January where students had the month off, but had to do some form of focused activity. One tour guide had studied tae kwan do, another ski ing in the nearby mountains and another girl from Africa (Uganda?) had worked in a health centre in her home country.
I was very impressed with the places we looked at, much more than I had expected to be if I'm honest, but my worry for DD is that if she is trying to gain admission to both UK and US units, she may fall between the two. I didn't find anywhere that was bothered about A Levels (small sample, there may be such places) as the focus was on SATs.