In my country, ticketing is per-venue. So if I want to go see an act at venue A, I go to their website and book from there. Acts' websites have lists of venues and dates, and direct people to the venues' websites to book. Most venues - at least the ones hosting things I attend - are independent of one another.
This doesn't seem like a natural monopoly to me - a new startup can sign up venues one at a time. Is the situation different in America?
That was the situation, but they all signed with TicketMaster because TicketMaster had the best point of sale software for tickets. Technically ticketing is still per-venue and they are independent, they just all use TicketMaster.
This isn't always 100% true, as some venues have similar owners, but that's a bit beside the point.
This doesn't seem like a natural monopoly to me - a new startup can sign up venues one at a time. Is the situation different in America?