I don't know that much, just public knowledge. As I said, unfunded liability isn't real debt, it's potential debt. No doubt foreign countries will hold some of it. China currently holds approx $800 Billion is U.S. debt, mostly in the form of Treasury bonds. Russia holds approx $125 Billion. Total U.S. debt held by sovereign banks is approx $3.4 Trillion. I assure you that foreign banks will not lend us $120 Trillion. The money to do it doesn't exist in the entire world and they would be insane to try. How much more these nations are willing to lend isn't clear. Inflation of the dollar may well drive them out of the Treasury game, but that hasn't happened yet, although China, for example, has been making a lot of noise about our excessive debt (while continuing to buy it up).
The only certain thing is that we're running trillion plus dollar deficits every year now and it's a disaster in the making. It is a crushing burden of debt and the money is mostly being wasted anyway.
BTW, I don't know where the author gets this number of $120 Trillion. I think he made it up. Unfunded liability, mostly Social Security and Medicare, is usually calculated at $53 Trillion (still a gargantuan figure).