Why would North Americans have more chance to develop cancer on the left side of their body?

In the UK it would be on the right side.

Americans have more of a chance of developing cancer on the left side of their body because we drive on the right side of the road and in the UK they drive on the left side of the road.

Expanding on the "why"

Its because of the habit of exposing the arm to the Naked Sun (was an article in the UK press about this several years ago)

You know the type well. Always drive with their arm out of their vehicle (trying to be "cool" ) Just thinking. If they did that all day, people would ask ..Yes? you want something? They'd be semi frozen in that pose eventually

Yes thank you both. Source

It was also mentionned by DR Oz on the Oprah show not too long ago ( like 3 weeks ago).

You are being a bit optimistic (or pessimistic) about Britain If you stick your arm out of the window here you won't be getting sun on it !Antibes maybe, most of the US maybe, but Britain?

"You are being a bit optimistic (or pessimistic) about Britain If you stick your arm out of the window here you won't be getting sun on it"

Fred, I heard that "acid rain" could be very nasty for your skin.