Spending 2% of GDP on the military is not a good use of $20 billion, every year!  Where do you think that extra $20 billion will be spent?  A good chunk will be spent on weaponry manufactured in the US, by US companies, MAGA.  
Talk about an economic black hole with no returns for Canadians in general.  Other countries must be thinking the same.  The world has greater needs than to support American military infrastructure.  
Trump is a buffoon.  Let him rant and rave, he will be on a new topic next week and leave more harm in his tracks somewhere else.  You can't change that.  Instead, Canada should continue with their patience and stick to what make sense for the country and our allies as a whole.  Canada and Europe will be strong enough in the long run to overcome this fool, and our patience will outlast the Republicans support for Trump as 2018 and 2020 elections become more prominent.  Trump's international sideshow has gotten bitter quickly and will only get worse over time.