Basketball. Which is commonly watched by people in the USA, Europe, and Canada.
Baseball would be the most popular sport between the two. More people play competitive baseball then basketball both in the USA and around the world
The USA soccer is the most watched sport in the world
Football, basketball and baseball
Football (NFL)Baseball (MLB)Basketball (NBA)Hockey (NHL)
The most significant sports for the USA are baseball and basketball. However, soccer and lawn tennis are now gaining popularity there.
I believe it was the most recent one XLIV