Considering paganism is a broad term used to refer to older, usually polytheistic, folk religions that predated Christianity, Judaism, or Islam, then Americans also have a pagan history and not just this neo-pagan movement you see today in which many people, raised under the Big Three monotheist religions, turn away and "go back to nature".
Unless, Sol, you're thinking of the Celts, in which case Celticism was overtaken fairly successfully by Christianity, although many pagan aspects still remain in the cultures. While their pagan traditions have been integrated into their lives, they were still practicing Christians, and Ireland is still extremely Catholic.
If your logic is that in order to be a "true pagan" one must have been raised in a pagan culture, then nobody in the Western world to my knowledge could be called such, because the forms of Western paganism were largely overtaken by Christianity. If, instead, you mean they should have "pagan blood", then many in both the US and Australia would also fit this bill, particularly America which had several influxes of Irish and Scottish immigrants in its history (I don't know Australia's history quite as well). But is it any wonder that St. Patrick's Day is a celebratory holiday in the US as opposed to the religious observance that it is in Ireland?
