There are some phenomena that are difficult to explain. Name two American acts that are doing as well internationally as they do in the USA. Lady Gaga aaaaand, no one else? Of course, when I say as well, I am only refering to those with big success. Not the ones that have average success in both the USA and the rest of the world.
If you look at the Billboard charts you will see only one American name that is loved outside the USA. (And what a name!) Why is that? Is her music more universal than that of others? Perhaps. But I think that a very important factor that led to her success was her unique style. She's confident, she's having fun, she works really hard on her videos and she has a weird taste in fashion (I bet you noticed that). She is not another Rap singer, nor another country singer and she is not another pop singer. She is a new category. Not because of her music but because of who she is as a whole.
One could compare her to Madonna. Sure, there are some similarities but Gaga seems different in that she does what she feels like doing. Her songs reflect her own experiences and if she seems provocative to some people, to me she seems true to herself.
Her rise to fame has been meteoric and that sometimes leads to a sudden fall. I can't predict the future but the present, inarguably, belongs to her.
"Where is the wolf? He and me could write a baaad romance"