You are right, ANY child born outside the USA, that's Father or Mother is a US Citizen, is a US citizen automatically. My best friend since 5th grade, married a Turkish woman while serving in Turkey in the USAF. Both his daughters were born in Turkey, but when he was transfered back to the USA, only his wife had to apply and become a US citizen, his daughters were born with dual US/Turkish citizenship.

So this surrogate thing may not raise any major problems after all, the "birth mothers" are not US citizens, but the "donor/father" and "donor/mother" are, which technically isn't much different from a father/citizen and mother/non-citizen situation.