score:3
Generally, the airlines are more concerned about your ability to enter the destination. Since you have a B1/B2 for the United States, that aspect is covered.
Keep in mind, since you are traveling from Montreal, 99% you will clear US CPB before boarding your flight as Montreal (Trudeau) has a Preclearence facility. Meaning, you will have already crossed the biggest hurdle before even boarding the aircraft. UA may do little more than glance at your travel docs, if even that.
If this is your first time entering the United States on that Visa, give you self some extra time as there are some formalities the Officers have to perform. Just answer the questions truthfully. Lying or even appearing like you're lying is much worse than merely sounding stupid.
Upvote:0
Johns-305 is correct in what he writes, but he does omit an important point. When you fly back to Canada the airline is going to want to see proof that you are allowed to enter Canada. That would normally be your PR card. Without that you may be denied boarding on your return. If you are allowed to enter Canada visa free because of your nationality anyway you may be OK, but otherwise this is a problem.