Holster, mag pouch, belt, range bag, tools >>> yes. I've done this flying out of TX. Gun parts, optics, ammo: technically NO. But you will be driving, so it will depend if you get checked by an American LEO to which you might or will have a problem unless you are in possession of importation documents. Canadian authorities might charge you taxes for the items you will bring in as long as you can prove that you can posses them legally. Provided no complete firearm or a part that needs registration as to frame or receiver, you should be good.
This is based on my last trip a year ago. To be on the safe side, check with CBSA and stay out of trouble. Border regulations changes every now and then.