Right. It's not existential, sure. It helps that all our debt is issued in our currency. But the fact is that ~30% of our national debt is held by foreign entities, and at the very least interest payments are an outflow of wealth from our country. This is not a healthy position if we value freedom of action. It WILL eventually constrain our country in meaningful ways. At the very least the mechanisms to manage this debt will weaken our currency, leaving everyone that doesn't invest in the market behind (which is a sizeable portion of our citizenry).

Pointing out that earth is a closed system so it's all good doesn't address these very real concerns about our unchecked national debt.