From what i remember mate, i used a link from the 'Top Rank' website (as it was Pacquiao Vs Cotto) that took me direct to the TicketMaster selling page. It was the US page, as we payed in dollars.
(Im not 100% certain but i think i had to make a account with the US ticketmaster website as my log in details i use normally for the UK site didn't work..may be an idea to try this out before you buy to save some time later on)
Everything went through no problem though, just made sure i read all the delivery options ect before confirming.
I had to print out and take my sale confirmation email as proof and also the bank card i used to pay. Showed them to they guy at the MGM collection point and he had my tickets waiting for me.
This was a few years back but id imagine thats still the routine for Tickemaster.
But yes mate, it was from the US TicketMaster page.