Also, to ppl who are mowing down forests before the kings men land, here's a tip from the developers of the game I found here: http://www.2kgames.com/civ4/colonization/tips/
Take the Fight to Them
The King's army is fresh off the boat and unfamiliar with the terrain of the New World. To represent this, they receive no defensive bonus when crossing mountains, forests or other types of terrain. This means it's often advantageous to attack them as they approach a settlement, rather than allowing them to attack you.
Using the Land to Your Advantage
The units of the Royal Expeditionary Force only receive combat bonuses when attacking your cities. They do not get any bonuses based on the local terrain. This means attacking the King's forces as they march through mountain passes will likely yield better results than simply waiting for them to lay siege to your city.