As long as your protein powder is legal in the United States (and Canada!), and security and customs agents are satisfied of this, you should have no problems.
I'd recommend that you carry the powder in its original container. However, if it's not practical, you could separate it out and perhaps bring the packaging label (or take a photograph of it). It's possible that the powder will be tested for drugs and explosives if its origin is doubted, and this may cause you some short delays, so make sure to build extra time into your travel schedule.
You should have no problem with reasonable person amounts. If you intend to bring in commercial quantities, you will want to research whether there are any special rules pertaining to importation, and will need to declare it accordingly.