We can explain this without "brainwashing": Risk-taking Canadians move to the United States, leaving behind the risk-averse. ;)
In reality, Canada and the U.S. have a "common market" of sorts that allows talent to move back and forth fairly easily. On top of this, cities tend to "specialize" in certain industries, and it's much easier to move the talent to the industry than move then industry to the talent.
This means that Hollywood stays in Los Angeles, and Canadian actors move south; Silicon Valley stays in San Francisco and Canadian programmers move south; Wall Street stays in New York and (some) Canadian Bankers move south.
>>In reality, Canada and the U.S. have a "common market" of sorts that allows talent to move back and forth fairly easily.
Unfortunately, it's not really a two-way net-zero exchange, but majority one-way from Canada to the US. This is the main reason that the brain drain has been discussed since, well, forever, but the earliest that an easy Google search refers to brain drain acceleration since '89[1].
To be fair, the US has been draining brains via the seductive American Dream from all countries around the world since it's founding, but it's particularly painful because of the cultural overlap that you referred to in your comment that make migrating down south so particularly tempting.
The (not) funny part is that some suggestions to combat brain drain is to aggressively increase immigration of skilled immigrants[2], which brings us back full circle.
Immigration will help (and Canadians begrudgingly like this solution because it also shores up the income-tax “hole” caused by low a birthrate/large retired population and generous social benefits to pay for) but it can’t fix the problem because it ultimately comes down to capital and risk: Canadian companies must service international markets in order to generate an equivalent return on investment that rivals U.S. companies in order for investors to be able to deploy capital at the same volume. If successful, it ends up looking more like “an outsized proportion of FAANG-sized companies are Canadian”, and less like “Canada has an equivalent company for every FAANG but each has an outsized return” because the latter is much harder to achieve, for various reasons I won’t get into.
In reality, Canada and the U.S. have a "common market" of sorts that allows talent to move back and forth fairly easily. On top of this, cities tend to "specialize" in certain industries, and it's much easier to move the talent to the industry than move then industry to the talent.
This means that Hollywood stays in Los Angeles, and Canadian actors move south; Silicon Valley stays in San Francisco and Canadian programmers move south; Wall Street stays in New York and (some) Canadian Bankers move south.