You'll be dealing with soldiers, not guards
The enemies in previous games have, for the most part, been city guards equipped with swords and other medieval weaponry. Obviously, the behavior of 18th century British and American soldiers is going to be different from what we've seen so far in the series.
For example, when you're a certain distance from a group of soldiers, they'll line up in an infantry formation when they spot you—just like they were trained to do. Taking human shields and ducking behind cover can help Connor evade their barrages of rifle fire.