Its the population density and tax regime. Usa has high enough population density to have real wealth pools and low enough taxes that those wealth pools can create new billionaires when they invest in good ideas. Europe could do it if they dropped their tax rates and crazy labour protections to get more dynamic, but i think the current rich there like that the system aborts new billionaires before they are born.

Its always what the greatest fool will pay. Usa has way more fools, at way more levels of company development leaving way more out opportunities. In Canada be prepared for 7 to 10 years slog to get to where you can list on a low scam stock exchange or be sold to an international company at a discount. Better hope nothing happens in that time to tak your 10x to 100x return to zero. Vs usa if you have strong growth or strong cash flow you can usually get out within a year of starting to earbestly look no matter what stage you are at usually without the discount applied to being a Canadian company. The only things that make sense to do in canda is resource extraction and cheaper north american holding of foreign workers us companies dont want to leave in the third world but who cant get into the usa and canada has not yet impoverished itself enough to get the idiots in the east that control everything to allow major expansion in that. Basically this place should be a no go for startups except for very rare exceptions.