Assuming that you're declaring to be a non-resident (NR) in Canada for tax purposes, the ideal scenario would be:
- You notify your bank that you are NR.
- Your bank withholds the appropriate amount of taxes for you on the investment income, and issues you an NR4 as opposed to a T5.
- You would input both the income and the taxes withheld (as foreign taxes paid) on your US tax return, which essentially is just for reporting purposes and would not subject you to additional tax (because of the foreign taxes paid to Canada already).
- You wouldn't have to do anything else on the Canadian side if you had no other income here.
Since you said you received T5s, your bank probably doesn't know that you're an NR and thus didn't withhold taxes for you (you should notify your bank now for the entire 2011 if you plan on remaining as an NR, and the above scenario would apply - makes things easier). As for this year, check out this link for the Canadian side of things:
http://www.cra-arc.gc.ca/tx/nnrsdnts...nrs-eng.html#f
Looks like you're okay on the Canadian side as long as the interest is from an arm's length party. I'm not too sure about the US side of things, but hopefully that helped.