If anyone is interested in the question of where the US fits in comparatively on the question of birthright citizenship the answer is: we are in the distinction minority. In terms of comparison to other highly developed states only the US and Canada have birthright citizenship. On a geographical dimension, the practice is common in the western hemisphere in general, but not in the eastern. This latter fact is not surprising at least vis-a-vis Latin America given the heavy influence of US constitutionalism on those countries.
There are two sources to investigate. First is a study done at CIS: Birthright Citizenship in the United States: A Global Comparison. The second is NumbersUSA, which has a slightly different set of countries.
I am insufficiently expert on this matter that I could not, at a glance, say for sure which dataset is the most accurate, but the NumbersUSA set is newer. I did use the CIS study in A Different Democracy and recall being convinced at the time that it was adequate.
One thing is for certain: this is one of those areas in which the US can claim to be somewhat exceptional.