I'm 'nesting' a trip to Canada during my trip to San Francisco and points beyond. Obviously when I check in for my Westjet flight I will have the return portion of the I-94 stapled into my passport. Will it be removed and will I have to fill in another one for entry to the US? Or what?
The last time I went USA-Canada-USA was in 2004. Then you retained you I94-W and Canadian Immigration stamped your passport.
It may have changed though.