traveling abroad with isize

We will be traveling to America with our 7 month old to visit family and I wanted to bring our cybex sirona m2 isize car seat with us to use. I have read that all though a car has isofix that isize may not work correctly. Is this true? Our family in the US has a new car that has isofix and I want to make sure that our car seat works and is safe. How do I find out if an American car will work with out carseat?