Wow! I just want to thank this site for the link I found to the U.S. Embassy's website as to this being a mandatory thing...
I never realised that it was mandatory really, but thought we would go into London 'eventually' and specifically to apply for our son a U.S. Passport (we have since applied for him a British one!)! We meet the 'transmission requirements' under the following clause:
"Child born in wedlock to one U.S. citizen parent and one non U.S. citizen parent on or after November 14, 1986: A child born outside of the United States to one U.S. citizen parent and one non-U.S. citizen parent may be entitled to citizenship providing the U.S. citizen parent had been physically present in the United States or one of its outlying possessions for five years, at least two years of which were after s/he reached the age of fourteen. This period of physical presence must have taken place prior to the birth of the child."
My son is 3 1/2 months-old...So, I guess he can already be a dual citizen then? His having a U.K. Passport on the way will not affect his getting a U.S. Passport as well then--nor his automatically qualifying for U.S. Citizenship as the son of an American mother?
I guess we will have to make an appointment very, very soon since a few months have already gone by since his birth and they say to do it, 'as soon as possible'! We do have a lot upon us at the moment with our moving to a new town in a fortnight's time, an illness in the family and a busy life overall. Heck, I love a good excuse to go to London and to, "Whole Foods" anyway! So to the U.S. Embassy we will go!