Questioning the country with the most tennis players in the World is not too bright imo lol
124 American players have ATP points, so it's kinda normal to have many tournaments there.
The Czech Republik has 3 challengers, 100K Prague, 42.5 Ostrava and 127.5 in Prostejov, so they are busy enough i guess.
Events that their #1 player can't play. Even when Berdych was outside the top 10 he used to make the effort to play at least a challenger every year there. They really do need an ATP event now.