Pretty sure there are 1 or 2 Canadian teams in the MLB. But the real reason is that Americans think they are the world or the very least the center of it.
the national teams of every other nation worldwide simply did not qualify. The qualification procedures are laid out clearly on the MLB website. Other nations are nowhere near the level of the worst MLB team.
It's not really a World Series. The name is to make Americans feel better about their baseball teams.
They're paying in the best baseball league in the world, by far. And many players are not American. There are many players from Latin America and Asia. The best from those areas often come play in MLB. I guarantee you there is no baseball team out there in the world who would say "we are better than the World Series champs" or league that would say "we are better than MLB."
I love America but I must say I have a lot of fun visiting and getting some pretty wild responses on where they think New Zealand is when I tell them I'm from there. I guess for Americans they have 50 odd states, a lot of them very different and almost like separate countries. That's a lot to keep up with so I can appreciate in some ways how that is the world to them.
Baseball struggle to attract fan base worldwide beyond USA, Dominican, Venezuela, Japan, and now even in certain pockets of United States for that matter…
Today many in United States don’t even know/understand many of the rules of baseball…don’t even know when ball crosses first or third base in fair territory and then goes into foul territory it is still fair ball.