You may be thinking of the "World Pool Masters." That is not a championship. That is an exhibition event. The promoter is free to invite whom he pleases. I see that last place paid only $1500, and perhaps that kept any Americans from accepting invitations, assuming some were offered.JAM said:... In the recent world championship in Europe, there were no American players invited -- NONE. ...
For the World Championships, there is normally a quota system for how many players each federation or confederation sends not counting ranked players and wild cards. This is set by the WPA possibly in negotiation with the promoter.