First – Canadians have no special privilege or right allowing them to keep their car in the United States for more then one year. If the Canadian car stays in the US for longer then the required time, the owner runs afoul of the US car treaty with Canada. The “US car police” can seize your car and sell it at auction or send it to be destroyed.
Second– If your Canadian car is in the US for more then six month – your Canadian car insurance policy becomes null and void. In my opinion, this is a far more serious consequence then having your vehicle seized. If you vitiate the terms of your Canadian car insurance policy and you are involved in a car accident, your insurer can deny you coverage. This means you become personally responsible for all of the financial losses, damages, personal injury claims, lawyers bills etc.