There are a bunch of extra states added. Think Colorado and Wyoming, the two rectangular states just east of the west coast. Now there are 4 rectangular states. Another example: just east of New York and west of Maine are Vermont and New Hampshire. Now there are 3 states instead of 2. It's like that throughout.
Bunch of extra states with similar shapes to existing states, so it messes with your eye and kinda blends in.
Might be harder to do with a map of Africa, Asia, Europe or south America because there aren't as many straight line borders and things are a bit more curvy.