It's true that environmental degradation and excessive government debt are very different. The environment is physical and debt is financial. But they're similar in several ways.
First, man-made environmental degradation and excessive politically-driven government borrowing can both wreck a society.
Second, both reflect reflect actions living Americans can take without regard for the well-being of future Americans because under our Constitution future Americans will have Constitutional rights when they're alive, but they don't have them now. The Constitution protects the interests of living Americans but not future ones. It's precisely this difference in how the interests of living and future Americans are protected that allows greed-driven living Americans to use lobbyists and political contributions to shape tax cuts, government spending, and environmental laws for their personal benefit.
Third, excessive debt and environmental degradation are both quite permanent. Once the environment is degraded it's extremely costly if not impossible to restore. Once U.S. Treasury debt is issued and the borrowed money spent, it cannot be eliminated. Those government securities are assets in the portfolios of millions of families, institutions, and nations worldwide. It's almost impossible to imagine conditions in which those families, institutions and nations would be willing to forgive the debt. No, they want the U.S. to make interest and principle payments on time without fail. If the U.S. ever does not make those payments, confidence in U.S. government debt will collapse. The result will be financial market chaos.