Its real interesting. We have also made exclusions to Chinese born in America in the 19th century. It was called the Chinese Exclusionary Act or something like that.
Here is a site with some info on it.
http://www.newswithviews.com/Vieira/edwin84.htm
http://www.theobamafile.com/ObamaLatest.htm
Read the US vs Wong Kim.
True, but that's an issue of US law. But the law of the UK, or any other country, makes no difference to the citizenship status of an American citizen.
In the Wong Kim Ark’s case in 1898, the Supreme Court used the term of “native born citizen” to described Ark’s U.S. birth instead of stating him to be a “natural born citizen”. A distinction made by the Supreme Court at the time that would only mean to be Wong Ark could not legally become President.
In US vs Wong Kim, the Supreme Court ruled that Wong Kim was a natural-born American citizen.
There were attempts to exclude Chinese born in America. They were rejected.