Depends on how you look at it.

Yes.  You are correct in a way.  There are a lot countries which have high Debt/GDP ratio.  China, Japan for example.  But China GDP is growing at 6 to 7% pace which is a lot higher than US.  We have been growing for the past 9 years at rate of 1.5 to 2%.  As long as you have a decent GDP, you should be able to service your debt.  That's why China can handle a higher debt ratio than US.  We can handle our ratio of 100%, that is no question about it.  But we can not handle if the ratio is too high .  Trump can not just do the tax cut without any incoming revenue.  Just use the 2% GDP growth is not enough to support his tax cut.  If the tax cut goes through, we definitely will see the increase of our national debt.