To divide New England from the rest of the colonies, the British could have used the physical geography of the region to piecemeal the region up and isolate each region from each other.
The key, would be waterways. The British Navy was one of the greatest Navies in the world, if not the greatest, and Britain would have been wise to utilize water based blockades with a few land-based blockades to isolate, divide, and conqueror.
As an example, Modern-day Maine would be portioned off via a river blockade at the Piscataqua River. Massachusetts could be split at the Berkshires using efficient blockades. Blockades on Lake Champlain could be used to split New York from Vermont and beyond. New York City could be surrounded by water, isolating an important port of commerce.
