Which two bordering states would change the most culturally, politically, economically, etc. if just a relatively small piece of land on their shared border switched hands?

When I’m talking a relatively small piece of land I’m thinking around less than 5% of either state’s total land area switching hands. Also I’m talking about land that would be a contiguous addition to either state. So not some city/land hundreds of miles away from the state’s border.

I’m thinking Cook County swapping from Illinois to Indiana would be a drastic change. Illinois would change from an economically important solid blue state to a Republican agricultural state. Indiana in turn would be an even bigger version of old Illinois. Even though roughly only 1-2% of either state’s land area was gained/lost.

Any other great examples of this?