I couldn't confirm this anywhere on the web, I am a TN visa holder and could only find the following information for tax purposes:
If you are an alien (not a U.S. citizen), you are considered a nonresident alien unless you meet one of two tests. You are a resident alien of the United States for tax purposes if you meet either the green card test or the substantial presence test for the calendar year (January 1-December 31).
From IRS web site (Determining Alien Tax Status).
So that would mean you have to meet either the GC test or the substantial presence test (you can do it by yourself) to determine if you are a nonresident alien or a resident alien for tax purposes. You would only be a resident alien roughly after one year residence in the usa.
So something changed from 2006 to now? or am I missing something?