Nothing. There is no border between the US and France.
The US state of South Dakota is the southern border of North Dakota.
Hawaii
The US state that does not have a straight line in any part of its border is Hawaii.
Honduras does not border any US state.
Hawaii is the only state out of the 50 US states that does not share a border with any other state.
In the US, Hawaii.
Alaska
It's Alaska, which is a state but doesn't border another U.S. state.
There are two: Hawaii and Alaska. Neither shares a land border with any other US state.
Kansas is the US state on the southern border of Nebraska. The capital city of Kansas is Topeka.
Monaco, a city-state located on the Mediteranean sea, has France as its only neighbour. The border is under 5.5 kilometres long. Monaco is the second-smallest state in the world, after the Vatican.