The reason why student debt is basically unheard of in Denmark since college is free (although to make that happen, the Danish government poses high taxation towards citizens like they do in order to maintain stable social security nets like subsidised healthcare and public housing, also why they have less homelessness).
Mainly Danish, Swiss and European citizens are eligible to study without stressing over student debt upon graduation. It stems from this: Danish government is more on for the people while American government is more on caring about themselves plus nepotism on the side (MORE & HIGHER TAXES TOO ON TOP OF THAT).
this misses what happened to public colleges, like the land grant colleges you mention. at the height of counterculture, campuses exposed everyone to powerful ideas that made them do all kinds of organizing against the establishment. for example in 1970 the Ohio National Guard was called onto Kent State University and fired over sixty rounds into anti-war protestors, killing four. Ronald Reagan became California Governor, defunded universities, and introduced tuition to stop this onset of class consciousness; in his words, to bar “undesirables” from college. then in 1975, NYC went almost bankrupt, and regretfully adopted the same measures upon the City University system in a ton of cuts to tackle $14 billion and growing in debt. thus the same policies spread across the rest of the US. a similar reason is why the “leftist” party in Britain managed to landslide against 20 years of Conservative rule by promising to introduce tuition.