Note that you may have to complete Form 1116 to claim the foreign tax credit and it sometimes can be limited by AMT rules and the 1116 rules, but then carried forward for unused portions.
I called the IRS to discuss the IRA question. Not much help. I also called Fidelity to ask about help with recovering Canadian tax for an IRA. They didn't know either. I have a call into Canada to ask about this Form NR7