If you prepare your spousal sponsorship application thoroughly and you can provide enough backup evidences to show a stable and long relationship, you have nothing to worry about. For most applicants from US with clean criminal records, the case will be approved as fast as less than 6 months. The one thing you need to think about it is either you guys want to apply a outland application or inland application. Both options comes with its own benefits and shortcomings. With a outland application, your future wife can stay in the States and can come to visit you as a visitor for the entire process. With a inland application, your future wife has to come and stay in Canada through the entire process (a short visit outside Canada may be OK), but she can apply an open work permit to work in Canada.