If you're poor, Canada is a pretty good deal. If you're middle-class, it's ok. If you're upper-middle-class (top 10% in income) it's better to be in the US.
It's not all about income, and it's really as simple as that. IIRC marginal tax rates in some parts of US are higher than some parts of Canada. So, as usual, it depends.
On average I don't think you are wrong, btw - but it's hardly cut and dried.
Probably obvious, but : and it's really not as simple as that.