Based on the popularity lists, I guess Irish people have only recently started using the name.
Erin is only a version of the original spelling
Eireann, so I would think it's not quite the same as an American child named
America.
2001 -
Erin was the 13th most popular girls' name in Northern
Ireland.
2002 -
Erin was the 48th most popular girls' name in
Ireland.
http://www.behindthename.com/php/search.php?terms=erin&popterm=&gender=both&extra=p