What other nations besides the USA have professional baseball?

There are many nations that have professional baseball:

Canada, Mexico, Cuba(Cubans only), Japan, Korea, Puerto Rico, Venezuela, Taiwan, Australia, the Dominican Republic, the Netherlands, China, Italy and Isreal. Im sure there are even more, but these are just some off the top of my head. While MLB is widely considered to be the top competition in the world, players from the Japanese, Cuban and Latin American leagues(Venezuela, Dominican Republic, Puerto Rico) consitantly out perform the US in international competitions such as the World Baseball Classic and the Olympics.

Japan, Cuba, Mexico to name a few

I would say the Cuban league would have the greater chance of competing against an MLB team. Japan has given us players such as Ichiro, Hideki Matsui, and tons of pitchers over the years (Nomo, Irabu, Matsuzaka, the list goes on) but the majority of players are not MLB caliber, and only a select few can make the transition.

Japan

Japan. im not sure i just know that is where Matsusaka came from. he came from some team called the lions. They probably aren't as good because Matsusaka did much better in Japan than he does here in the MLB