Tax questions for TN visas

First of all, I'd like to say a big hello since I'm new here. I signed up on this board to hopefully find help with a tax question I've been having, which HR is giving me very ambiguous answers to.

I'm starting an internship soon with a US company soon for a 12-week period. During this time I would be living in the US, and staying with a TN visa. I will have the US payroll deposited into a RBC US account.

For this tax year I will have payroll both from my current job in Canada as a research assistant and the payroll from the US internship. How exactly does the tax situation work for such a short US stay? Does my US tax credits transfer to Canada? I'm guessing I have to file tax reports for both countries in spring next year, is that true? How do I file a US tax report once I've returned here?

forums.serbinski.com is a better place for this question.

So I've asked this question on Serbeski, and for future reference, I've found out that you need to fill out form 1040NR