you have to be really really fast, the scalpers are glued to ticketmaster and buying them. I've already seen over 300 GA tickets on stubhub for my show
I think with all this demand, her team will be forced to add more US dates. That is, unless she wants to upset her fans since a lot of them still haven't seen her in forever given that most of the US dates for the Born This Way Ball were canceled because of her injury.
Gaga's also benefiting from consistent airplay in the US for many weeks now, she doesnt have that in some countries so it could be different once international go on sale.
btw shes out of the top 10 in canada/UK from new releases. without a video, a song cant hold internationally. the monster is even down to #9 in UK now.