The reason for the Americans attack on Montreal was the British army will catch people from American merchant ship and made to serve for British navy.
Explanation:
The American attack on Montreal was to make the French-Canadian people to fight for American side in the war against Britain. The main reason of the battle was to take revenge against the British army who captured the
American merchant ship sailors and made them serve the British navy. American waged war to take control of the sea route from St Lawrence River to Britain and to move out British colony from Canada. Americans have succeeded in this attempt and captured Montreal.