Lets assume this is Trump Policy (or objective) - the likely hood of this happening is still very low. It might have gone from a 0.000000001% chance to a 0.0000001% - so yes its 100x more likely than before, but still very unlikely.

Imagine the scenario of Mr Trump manufactures an excuse and implements the steps sufficient to crush the Canadian economy (depression level) as a prerequisite "softening up" step to a planned takeover. Offhand I would put the chances of that much happening above 10%, eight orders of magnitude higher than your estimate.

It does not seem to be related to any negotiations or negotiating ploy based on the timing and the fact that he isn't actually asking for anything from Canada. He says he wants to annex Canada, he has been consistent on that point for a while, and nothing can stop him if he wants to, so the main alternative is that he simply changes his mind. Or becomes incapacitated. Obviously the fact that it was until recently unthinkable and illegal isn't a consideration.

Needless to say, this sort of thing is not good for the US economy, the returns of businesses dependent on its stability and health, the US dollar, or the US stock market. To the best of my knowledge there is currently nothing that matters more to the true intrinsic value of a share of Berkshire in the next 5+ years than the enthusiasms of the current president. And not just at the margin.

For example, Berkshire's revenues are overwhelmingly in US dollars. Berkshire's stock is down, not up, year-to-date, measured in almost any major currency other than the shrinking US dollar. But the markets are serving up fire alarm warnings.

A new war started today. Unsurprisingly there were ructions in all sorts of financial markets, but there was no "flight to safety" towards the US dollar--the day's range was the same as yesterday's, weakest in the last few years. Admittedly you have to have been watching the world economy pretty closely for the last few decades to appreciate how odd this is, but it's so unusual that it should be deeply troubling if you have any assets tied to the value of the dollar. It appears that people were selling assets, including US securities, but also immediately selling the dollar proceeds. Similarly, the yawning gap of the 1-year EUR/USD bill/bund yield spread has been the strongest predictor of currency movements for ages, but the massive 2.3% gap these days still isn't holding the dollar up, let alone causing it to rise. If Mr Powell were somehow convinced to cut rates, it might cut the lone thread holding it as high as it is. (or not--currencies are famously unpredictable).

Politics and headlines never matter to investing, except on the very rare occasions that they matter more than anything else.

Jim