I was raising this point more as a sociological observation. What interests me is to understand why Americans are apparently the only people in the world (as far as I know) who have come to use regularly (one quarter of the most popular baby names in the last few years) old traditional family names as given names. It is doubly interesting because:
1) All the surnames used as given names originated in the British Isles, although only about one third of the American gene pool descends from that region. Why aren't there any Scandinavian, Dutch, German, Polish, French, Italian or Spanish surname used as given name, even though all these people represent a bigger part of the ancestry of American people than the British Isles ?
2) British and Irish surnames rank among the world's oldest family names in continuous use. The British Isles are arguably the first region to use surnames among the whole population, as opposed to the elite only (like in Asia or ancient Rome). Celtic surnames are the oldest, and many originated in clans' names.
Americans also differ from Europeans in the ease with which they change their names (both given and family names). It's extremely easy from a legal point of view to change identity in the USA, while it is nearly impossible in most European countries (the UK being in exception, although it is rarely done in practice). This attitude denotes a certain contempt for one's origins and familial heritage.
Historically, a lot of migrants to the USA left their home country to start a new life, often cutting ties with the past. Many Europeans changed their names when they arrived in the USA, typically Anglicising it or choosing a brand new English-sounding surname.
British and Irish settlers were the first to arrive in the original 13 colonies, and many of them lost all track of their ancestors' origin. So much is obvious from the
US ancestry census, in which the majority of the white people in the Southeast USA described their ethnicity as 'American' because they didn't know or couldn't identify anymore with the country of origin of their ancestors (typically British and Irish settlers from the 17th and 18th centuries).
It would be enlightening to see if the use of British/Irish surnames as given names is more widespread among those "ethnic Americans" who lost touch with their origins, or if, on the contrary, it is more common among people of continental European origin who try to adopt more English-sounding names. I would guess the first.