Well they don't seem to want to be an ally anymore and infact they seem to want to be Canada's enemy.
So we'd have to now form new alliances and stop putting all our eggs in one basket.
Diversify trade, form new bilateral relationships.
Yes, the US will still have the majority of power and clout for the foreseeable future, but if they continue on the path they are on, they will gradually weaken themselves and help countries like Russia and China fill the void.
It will happen naturally as they continue to piss off and alienate their friends.
You seem intelligent, so I'm forced to conclude that you're not being honest in your assessment. The US is not trying to break our alliance. They are trying to get us to pull our weight on NATO spending and border security. Their positions on those issues are, in a word, reasonable. Why shouldn't we pull our weight?
You can yearn for a better relationship where we don't have to pull our own weight, but frankly the US, for all her imperfections, is the best looking girl at the dance.
Your admiration for diversification is superficial. Not all trading relationships are equal. You can't equate a trading partner in close transport proximity, over a well organized border, with relatively uncorrupt bureaucrats, police, and legal system compared to what most of world offers. Talk to business people who deal with China and hear about local corruption, payment difficulties, forced partnerships, and a legal system that is simply a sham in the event of disputes. These aspects simply aren't part of trade with the US.
Show me a better trading partner than the US and then we'll have something to talk about.
p.s. The most recent, and best, opportunity to open a significant new market happened when the Nord Stream 2 pipeline was taken off line. However, our Liberal government couldn't divorce themselves from Quebec politics to get LNG pipelines and terminals built to the Atlantic for sea transport to Europe. If we couldn't seize such an easy opportunity, how do you suppose we're going to develop the new trading relationships that you're dreaming of?
p.p.s. If we really want to end this talk of annexing Canada, all we need to do is tell Trump a lot more about Quebec!