Debt is about trust.
Japan has the highest debt to gdp ratio, but that’s not a problem because we trust it. With enough trust you can go pretty far. There are a lot of trust factors for the US, like its military or the petrodollar.
By "how much material is being dedicated toward...[it's]...future existence" you presumably mean how much the firm or individual is investing in relation to their income or some similar measure. That can be part of it, but definitely isn't all of it. All market transactions are, contrary to the technocratic worldview of mainstream political economists, human transactions. The actual underlying human relationships matter, and the balance sheets only matter inasmuch as they facilitate communications between actual people.