Americans based in Canada do not get work permits, all that I know of commute to YYZ. The pay difference, yeah it sucks, I have been with CX for 2 years on the freighter in the US and make 72,500USD while these new guys come in and get paid 92Gs and get better trips, while I rot in ANC in each direction.

Tax free income is only if you work and reside abroad. If you live in the US then you are responsible for US income as well as you state's tax, on your entire income.

FO