When I entered Canada with my wife and my son, At the airport, we took pictures, fill some forms at two offices. I told the Canadien immigration officer at the airport, we were going to return to USA after tommorow.
I was asked: How many money do you bring with you?
My Answer: $300, it is for my these two day's expense only. But I told her the $number in my accounts.
we were told "you are Canadien permenent residents now".
We can go back to USA that moment. The mapple card will be sent to my friends' home. But we stay there for two days for the Social security card.
Two days latter, we steped in the queue for entering USA.
1) I was asked to fill some simple forms
2) then I show my H1-B visa, Passport with I-94, and the filled forms
That's all
Very simple and easy.