The reason that the U.S. can keep functioning despite being trillions in deficit is that other countries think of our nation as a safe investment. It is the only global reserve currency which enables us to actually print money without causing runaway inflation. We enjoy this status not only because of our military strength but because of how the world sees us.
When Trump erodes our hegemony in the world, by ceding leadership to other countries, he erodes acceptance of the U.S. Dollar as a reserve currency. The day that happens and our currency becomes devalued, we lose any claims of exceptionalism.