Ambery, you will want to supply the residency/registrar's office with the form and complete documentation showing a) that you've permanently lived in MI/ US; b) attended school in Mi/U.S.; c) have Green Card in good status; d) own property or pay taxes in MI; and e) hold no further ties (no bank accounts, don't own property) in Canada.
My son is a Canadian citizen by birth who attended middle and hs in the US, lived here, worked here, had a valid green card, etc. and had to go through the process. In the end, it didn't hurt him in terms of admission; and in the end he was rightly declared in-state.