I'm a Canadian citizen, but a non-resident (I live in the US). I closed my RRSP account - how do I report this income? I haven't received a T4RSP form.

If you closed your RRSP account you would have had to move the money into a non-registered account (a withdrawal). So, you should have received a T4RSP form. Check with the financial institution where you had your RRSP to see how to get a slip.