$4.1E12 isn't really that difficult to relate to. Just amortize it across the US population of 325 million. That's $12,612 per citizen. It's also about one year of Federal spending.
It's a negative thing. Both individual debt load the and the rate of delinquency has been increasing, with student debt being the worst of these; if you can fog a glass you can make the Federal government send money to some school against your future earnings. There is probably no form of debt easier to assume in the US and upon this river of money floats a horde of careers, bonuses, pensions, endowments and gold plated benefits for The Great and The Good of academe, which makes questioning the value of it all a political third rail.
What do economists think? They're watching the bubble grow and devising ever more contrived ways to pretend it's not a bubble.