@ali21471
States have agreements with other states. I don't know every California tax law, but I doubt California has a private agreement with Canada or your province. (I don't even think a state could legally make an agreement with a province. That seems to violate the US constitution, which puts treaties exclusively in the hands of the federal government.)
For your federal tax return, "foreign taxes" include taxes imposed by the Canadian government as well as your provincial taxes.
A foreign country includes any foreign state and its political subdivisions. Income, war profits, and excess profits taxes paid or accrued to a foreign city or province qualify for the foreign tax credit.
https://www.irs.gov/individuals/international-taxpayers/foreign-taxes-that-qualify-for-the-foreign-t...
This may help up to a point. Your maximum US credit will be whatever your US tax was. In other words, if your US tax was 22% and your Canadian tax was 25%, adding provincial tax will not get you a bigger credit on your federal return. But if your US tax was 22% and your Canadian tax was 20%, adding your provincial tax might bring you up to the 22% level (the US credit will never be more than the foreign taxes, but the provincial taxes are included in "foreign").
But provincial taxes won't reduce your California state taxes.
