Not sure how one would measure "access" though, does that mean counting people who could have reasonably gone to college but didn't?
If you consider the total cost of attendance including room, board, books, and other costs, the estimates for the most expensive schools peak either at $68--72k/year at Columbia or ~$70k/year at Harvey Mudd, followed by at least 40 other schools over $65k/year.
The most expensive in-state tuition at a public college is $16--17k/year. The most expensive (in-state) total cost of attendance are a few schools (like NJIT, William&Mary, and some UC campuses) in the $30--34k/year range.
From a policy perspective that kind of long term debt comes with stress, health problems, productivity problems, social mobility problems.
Peoples ambition (and in some cases sense of entitlement) comes from their upbringing; if you add long term debt to that aswell you end up in a situation where even more careers are decided by childhood circumstance, rather than potential.
I don't see how this could be stressful even if I continue paying some small amount into my 50s - from my point of view it's not debt, it's more like paying a water bill each month.
For example; a starter salary of £28k would be only £7k over the threshold and "only" result in repaying 9% of that, or £630 per year. But in Austerity Britain people on that kind of salary (e.g. nurses) are already starting to resort to using food banks.
Weigh up the alternatives, such as an apprenticeship or a job offer and university starts to lose ground to other options; but much more so for people with a lower socio-economic background. This is the problem.
Some people will look at the associated debt issues and decide it's not worth it (open question as to what percentage). Often this will be in comparison to a job offer or apprenticeship.
There will also be people who don't look at the issues directly, but instead rely on the guidance of older generations, and perhaps contrast things like living costs.
These decisions are made differently based on socio-economic status. That's the access issue.
I don't have objective data but there's plenty of anecdotal evidence around of people from lower-income backgrounds making choices because of their background not because of their ability.
https://www.theguardian.com/education/2015/aug/17/teenagers-...
For comparison, Denmark lists 0.95 years, UK lists 0.96 years.
PhDs and masters are also absolutely monstrously long in the United States - often literally twice or three times as long as in Europe. Fewer people do those of course but maybe that also adds up to a higher average.
In places like the UK you normally go from zero degrees to PhD in six years, while in the United States you could conceivably only just be fishing your masters work at that point.
Mind you this was in an engineering department in the late 80s and early 90s - things have no doubt changed :-)
As another extreme, I have a colleague who completed a PhD with very strong research results in Austria in just two years.
I'm from Austria and we switched to the bachelor master thing just briefly before I started to study. Before we usually had 5 years diploma studies and a doctorate with at least 3 years.
Another interesting difference is probably that our studies tend to be completely specialized. So when I studied CS I did only that. If you're interested in history or whatever you just study that in parallel - no tuition and for long we also had no access restrictions - you basically just went there and said you want to study X. 10 minutes later you were enrolled.