It might be worth noting that America is not the United States. America created states which formed the United States of America.

Re: eagles
Rome also had the symbol of the eagle. But the United States of America in particular has had the symbol of an eagle with outstretched wings. The UK is a conglomeration of kingdoms of England, Scotland (and Northern Ireland) respectively rather than a nation. It is worth noting that original doctrines of Christ came to the British Isles and Ireland approximately four hundred years before Roman Catholic missionaries came. Also, the monarchies or sovereignty of the English was not necessarily derived from William the Conqueror since sovereignty existed in England before 1066.