To be clear, it's not that there aren't startup founders who are Canadian citizens. But, in my experience, they tend to
move to the US as well—not for the tech talent pool, but rather for access to "proper" VCs. Canada has been creating startup
founders for a while now... it just hasn't translated into Canadian
startups.
Meanwhile, these startup founders often come back to Canada after getting their startup off the ground in the US... to create a Canadian "engineering branch office"—i.e., to hire tech talent at the cheaper Canadian going rate. But, of course, this only happens for startups that manage to get to a stage where they need whole offices of additional tech talent—which is not most startups.
Given this dynamic, I wouldn't expect increasing the number of available developers would do much at all. Now, if you could come up with some way to keep entrepreneurs from moving to the US, that might help...