183 days rule for tax residency, 10k/day exemption, and international tax credits.
The NHL schedule ensures that Americans on Canadian teams do not have to spend more than 183 days living in Canada, which means that they are able to claim their tax residency outside of Canada. Players earn their money across four different provinces and sixteen states. Some American cities even have city taxes on income.
Playing one game against every team, even if it takes two years to do a home and away, helps taxation parity within the league.
I'll baseline American resident playing for an American team at 0, and then the other combinations relative to that in a percentage. This is derived from Buffalo and Toronto.
1) American resident playing for an American team: 0
2) American resident playing for a Canadian team: -2.4%
3) Canadian resident playing for an American team: -8.5%
4) Canadian resident playing for a Canadian team: -4.2%
If you're playing in Alberta or BC, you're even closer to Scenario 1 due to taking home more money from lower provincial taxes.
If you're playing in Florida, Nevada (!) or Texas, then you're laughing your way to the bank. If you're a Canadian resident playing in a state without income tax, you're paying about as much as you would in taxes were you playing in Canada.
So we do have a signing disadvantage for American players, but it's not severe. Most people would sacrifice 2.4% of their total pay if it were the difference between unrewarding and rewarding work (or no playoffs versus playoffs) and a good quality of life.
American teams trying to attract Canadians who want to spend their time off in BC are at a bigger disadvantage than we are--unless they're one of the three aforementioned states.