Well, let's see and this is all MAYBE, and just one scenario of many possibilities...

There wouldn't have been a "Luisiana Purchase"

The Colonies would not have developed into into the wealthy industrial nation that the States was in the Twentieth Century.

Then Britain would not have had a Big Brother across the ocean to come and help out in two world wars.

The Battle of Britain would have been lost without the American supplies that were shipped across the North Atlantic.

The Axis Powers would have won WWII.