Good thread leo-j!
I'll try to explain (while adding some bad ass context).
Back in the 90's, the local music industry in america had complete control over what they wanted to promote to the average american teenager. It was easy for them to hype genres like Grunge, Rap, Hip Hop, Pop, R&B. They controlled the entertainers and their careers (however they were not able to control DJs and independent 'channels' and progressive artists from Belgium, The Netherlands, England, Italy, Germany and France), so they basically milked unaware american locals of their cash while keeping all the new fresh 'electronic' sounds away from MTV and the radio stations.
These days americans have access to Electro, Trance, House, Techno, 'Electronica' and other genres through the internet and are gradually being exposed to all aspects of popular music. Their mainstream music is naturally being influenced by this.
Lady GaGa is just one of many artist who borrows "new" sound from the different Electronic Music Genres.
Quality info with Sound Samples: Ishkur's Guide to Electronic Music (Flash)
WARNING!!! Seriously good link above ^^^
