relationship between trade deficit and national debt?

Answer 1

Government deficits tend to result in heavy borrowing, which raises interest rates and tends to discourage domestic investment.

A glance a Mundell-Fleming will demonstrate that this causes a trade deficit as well.

They tend to be related.

Answer 2

The only relationship is that a foreign entity that receives U.S. Dollars from selling exports to the U.S. will often choose to spend those dollars buying U.S. Treasury bonds, rather than do something else with them.

However, the trade deficit does not CAUSE the national debt, which simply results from the government spending more money in the annual budget than it collects in tax receipts.

Should add -- think of the opposite case (vs. US) of Japan. Japan keeps running a truly outrageous gov't deficit and a total debt the likes of which we in America would never dream of doing and couldn't achieve in our most profligate efforts. Yet they maintain huge trade surpluses year in year out. So go figure, the two largest economies in the world both have large national debt but with exactly opposite results on the trade balance.