How does all this look to the federal government and deficit spending? What happens when they can't borrow money at near-zero any more, and need to borrow more

How does all this look to the federal government and deficit spending? What happens when they can't borrow money at near-zero any more, and need to borrow more money at 5-10%? Everyone always said the debt was nothing to worry about. It's been repeated for a long time as our debt keeps rising, but it was most apparent with the recent spending bills and virtually no pushback on trillions in unfunded spending.