the USG regulations are not country specific but apply to US citizens around the world. in many of the countries that i have lived in (mostly 3rd world) people are happy to register their kids as US citizens, and in many cases count on the US embassies to provide security in emergencies (medical, war, etc). It wouldn't make sense to let US citizens from these countries bring kids with local passports to the US without question, it could be difficult to prove relationship to airlines and US immigration folk. Many 3rd world countries lack the local infrastructure to even do birth certificates, so you could imagine numerous problem scenarios involving kidnapping, adoption fraud, etc. I would assume that the USG's way of pre-empting these issues was to make in-country registration mandatory for those US citizens who chose, for whatever reasons, to live their lives outside of the US. It would be nice for there to be some exceptions made for countries like the UK, but i doubt it would fly post 9/11.