The US is currently at $1T+ a year in tax revenues that instantly go right out the door toward paying bond interest. It will likely be $2T within 10 years, even fewer if rates don't come down in that time. It's compounding and therefore exponential.
Situations like Japan are even more dire. A small increase in the interest rate results in a HUGE increase in interest expense at 260% debt to GDP ratios. Worse, their population is naturally shrinking a million people a year on account of their decades-long birth rate implosion. Hard to outgrow that.