I landed in Canada 7 years ago. So I don't know if the policy changed. If you plan to go back US in 30 days, you'd better not to submit you I-94 to Canada side. I think keep your I-94 will give you one more option if you change you mind. Otherwise you have to get a new US visa to enter US. Don't change your US license plate until you decide to live in Canada because everytime you across the border they will ask where you live.