This is the list of leagues and will be continuously updated as I add on to this:
UNITED STATES BASEBALL LEAGUE (US/Canada)
Tier 1: Major League Baseball (MLB)
Tier 2: National Baseball Championship (NBC)
Tier 3: American Baseball League (ABL)
Tier 4: Frontier Baseball Association (FBA)
ANZAC League (Australia/NZ)
Japanese Professional Baseball Organization (JPBO) (All thanks to tehsuigi)
The Euro Leagues Leagues separated by country (i.e. Paris is never playing Liverpool)
British Isles Baseball League (British Isles)
Championnat National de Baseball (France)
POTENTIAL LEAGUES YET TO BE MADE
Leghe Italiane di Baseball Serie A-D (Italy) Not in the game as I've yet to find a template for it. Might have to make it myself.
Canada
Benelux League Got the cities, just need to get names.
Korea
Caribbean and/or Mexico Probably might just steal 20_range's Liga del Caribe ATP
India
Iberia