Yeah, most NFL stadiums hold maybe 65-75k. There are 20 stadiums with an official capacity of over 80,000 in the NCAA (only 3 in the NFL). One of the main reasons the crowds are so big is that the universities are much, much older than the pro teams typically. There's more tradition built in.
Don't forget that the US is also a lot bigger and universities are more of a community than in the UK. US campuses dwarf anything here and by the same token you get more money there. Can't imagine a university here having more funds to spend on sport than a football club, plus the football club is a bigger foundation of local community here.
In fairness, we're a bit weird here, most European clubs are sport clubs with a multitude of teams represented, like Barcelona will have basketball, handball as well as football. Even volleyball.
There are some boss videos on Youtube of PAOK and AEK fans at basketball games going mental. Lech Poznan get hundreds turning out for their Under-12s!