Probably on US bases with schools, but I never saw a European play football when I lived there.
Because you play it with your foot that's why it's known as football outside of USA.
There is no American Football around the world because it is not popular outside the US
The Negro leagues were US professional baseball leagues. The term is usually used to include 7 leagues, also called "Negro Major Leagues" which began in 1920.
There are too many to count. There are dozens and dozens of basketball leagues, a few American football leagues, soccer leagues, many baseball leagues, and so on. There is no kept count of professional athletes.
There are many soccer leagues in the US. Anybody can play soccer no matter where they are or how old they are. There are club teams for children and adult leagues for adults. You just have to search around and find out what leagues are in you area.
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Why not? There are now over 100 teams women's tackle football teams in the US. The most common response from a doubter after seeing them play - "Wow, it's real tackle football!" In the main women's tackle football leagues in the US it's full gear, full tackle football, just like the men play. The only difference besides being women vs men is the women typically play with a smaller ball (the junior or youth version.)
Other sports are more popular, and nobody really wants to care about it anywhere else.
because no other country can be bothered to play American football Because no other country can compete with NFL teams in American Football. The same reason the World Series champion is called the "World Champion" (though, in the case of MLB, there is one team, the Toronto Blue Jays, outside of the US). Moreover, the title "National Champion" is used by the champion of COLLEGE football, and is thus unavailable for the champion of professional football.
The governmental authority for sports management is a non profit organization that is in charge of the testing of performance enhancing drugs. They test the US sporting leagues. This would include soccer, baseball, football, hockey, etc. They do the testing and results.
There is a professional womens league currently playing in the US called the IWFL. Also no major professional leagues have rules against women playing, but no women have ever played for any of them.