Why do people say that America is far more "religious" than any other part of the developed world?

For a start, religious attendance in the Republic of Ireland is HIGHER than America's. And if that isn't enough proof, why is it that Most Americans support abortion while here in Ireland, not only are the majority of us pro-life, but our constitution has it that Abortion on demand can't be introduced unless in a referendum? Our current law also bans abortion unless the mother's life is in danger.