It is going to cost around $1 trillion just to service the interest on the US national debt this year.

Can somebody please explain to me how this is sustainable in the long run?

As interest rates continue to rise it is only going to cost more to service the debt. This is all going to end very badly one way or another. The world sees what a mess this is and is racing for the exits as fast as they can. They want no part of the collapsing ZOG empire and the US Dollar that helps sustain it.