Flygirl
With a US passport you have a real opportunity to use the US system to your advantage.
Just do what the other Americans do. Get your FAA Commercial/Instructor ticket (lets guess at $25k and 6-12 months) and then instruct for 12 months. That will get you to 1000 hours single/100 hours multi, where you can get a job with the regionals. After a few years flying for Mesa air or something similar you will be ready for the majors and your first 737.
It's during your flying with the regionals when you will pick up your FAA ATP. If you wanted to fly in Europe you would need to convert your FAA ATP, but with 500 hours with the regionals this should be relatively pain free.
Of course this was pre 9/11. I'm not sure what the score is now. People on the inside are saying things are picking up, but those insructors where I hang out and who were looking for airline work last summer are still there.
Any more, just ask.