I suspect that's the reason then. In the US college used to be similarly affordable, but costs have gone up this past 10-15 years in most states. And in some states long before that. I had friends at Georgia Tech that came from Pennsylvania because out-of-state tuition at GT was cheaper than in-state in PA.
I was actually interested in going the college in the US at one point so I researched it a lot (and even spent two weeks visiting a few). If I remember right international students pay out of state tuition and the places I looked (UW campus') went from around $20,000 to $35,000. Not sure about in-state prices but they would have been much cheaper and quite comparable to the UK. Is it more a problem of students wanting to leave their state to study? If they stayed in state it seems like a college fund wouldn't be necessary (of course with exceptions such as the one you mentioned).
In general, yes. Students going out of state drives up their costs sometimes 2-3x higher than staying in-state. With some exceptions like PA where going out-of-state might be cheaper. I really only know PA as being particularly expensive because I knew so many people from there. I'm not sure what the current list of affordable states and unaffordable states are.
