Problem is that the Canadian 1% makes substancally lees than the US counterparts.
The Canadian 1% have an average income in 2014 of $466,700 cdn (Median is 313,000).
Wow that's a lot of money except the US average in 2014 is:

"The Washington Center for Equitable Growth put the average household income for this group at $1,260,508 for 2014. "

Holy Crap that three times the Canadian average if you convert into Canadian.

If you have a progressive tax rate that also means that the US tax base is substancally larger than the Canadian one.