If you take the letters of WHOTFAMI and remove the letters of FATHOM (i.e. [take] 'fathom out' [of] the clue), you are left with the letters W and I.
This fits the background to the puzzle, because...
The WI was founded in Stoney Creek, Ontario, Canada, by Erland and Janet Lee, as a community-based organisation for women. Further branches of it can these days be found in the UK, South Africa and New Zealand.
Who can join?
The clue's in the name - women! (Over the age of 18...)
You are 'Commonwealth Games' previously known as 'British Empire Games'.The Game was founded by a canadian journalist called Melville Marks Robinson. The countries which were part of the british colonial empire took part in the games.
Today 54 countries are part of commonwealth games. The four countries mentioned above are the only countries that participated in every commonwealth games conducted every four years.