Trump is making 50 billion dollars of cuts to non-defense programs and increasing the military budget by 50 billion.

If Canada would pay its agreed upon fair share for NATO  that would equal nearly half of the U.S. defense budget increase. 

What Trump is saying is that Americans are disappointed watching countries like Canada sticking the U.S. with its bill, 20 billion every year for Canada alone. Then diverting that money to your domestic programs while Americans divert from their domestic programs to pay for military.

"When the check arrives Canadians are nowhere to be seen" is a well worn cliche. Leaving a cheap tip in restaurants seems to be a badge of honor. Refusing to pay the NATO bill in the form of  a larger defense budget is more of the same.