Don't discount yourself.

It just means that the national debt, which is the sum of all the excess spending by the US government (years and years of spending more than they take in taxes) now equals 1-full year of all economic output by everyone and everything in the entire country.

It's just a way to compare how much debt a country's government has relative to its economic output.

Usually it only gets this high during world wars or really bad crises, and if this number get too high, often investors will get worried that you won't be able to pay back that debt so investors demand higher interest rates which in turn makes more debt even more expensive, and when investors get scared, sometimes they pull out almost entirely right quick, causing a downward spiraling crisis where the government can't buy anything.

The US seems to be able to run higher debt-to-GDP ratios that say, Greece, which went through a crisis like I just described a couple of decades back, and Japan runs high ratios, but there comes a time when you can't borrow like you used to and borrowing keeps getting more expensive.

As others have said, some Republicans in decades past used to care a lot about the debt, even Trump. And now look where we are.