Why do Canadians think Canada is a viable country? Countries to be considered countries need to be mostly self-reliant, not dependent on another for survival. If we banned trade, Canada would go bankrupt bc you wouldn't get to offset your losses.

Smuggling would become big business as Americans suddenly crave the essentials and luxuries on which the country depends. Very DPRK (you may need to google that).

If the borders were suddenly sealed like North Korea, the US would very quickly realise that it cannot be self reliant, at least while maintaining the American lifestyle.

Within this global economy the US consumes so much stuff it needs these foreign countries to keep selling to Americans. Trumps tariffs are a tax on Americans for wanting stuff from other countries.

What explanations do flat earthers have for the shape of our planet? If they do not have any, why should their opinions on this topic be considered credible?

I think you fail to grasp two things here:

In just one month, the US has gone from world leader to wannabe dictatorship. I sincerely hope you find the economic isolation you appear to crave.

Canada is currently over reliant on one major trading partner, which until recently was fine as we had a trade agreement which worked for everyone. However recent events have made Canada reevaluate its position and dependence on the US and the result will be detrimental to all concerned. Canada will realign with more reliable trading partners and wean itself off the US dollar.

In England, there's a small city called York which was named after New York. Why wasn't London, the largest city in England, named after New York? Why York?

the global economy is truly global. The only country that tries be entirely self reliant is North Korea, and that’s not working out so well.