Birthright citizenship in the U.S. is hardly about a desire to "extend rights and privileges to outsiders". The 1866 law was voted during the Reconstruction after the Civil War, to guarantee civil rights for Blacks [1]. It was later introduced in the Constitution to make it more robust against repeal [2]. Republicans have talked of repealing the amendment precisely because it is used (abused) by "outsiders" [3]. I'd like to see better examples to support the assertion that the U.S. has been more liberal towards outsiders than nearly any other developed country.
[1] http://en.wikipedia.org/wiki/Civil_Rights_Act_of_1866
[2] http://en.wikipedia.org/wiki/Fourteenth_Amendment_to_the_Uni...
[3] http://www.washingtonpost.com/wp-dyn/content/article/2010/08...