The Whole World In Your Hands

Good plan. You will effectively destroy all farms and food in England, and they will all starve to death. Perhaps not the quickest way to win, but as we all know, a sloth would kill a wolf.

You send in American soldiers with orders to set aflame any farms they see. But a problem arises...they find no farms. Duh! Britain is known to have the worst food in the world! They must import all of their food!

And now you have told Britain of your true intentions. And they usually don't like people who want to kill them. You are no exception. England and Spain join forces to assure your demise.
End Of Story