@jerv It seems to me that the territory versus state issue was just a last-ditch effort to make voters wary of Obama. Hawaii was already a state by the time Obama was born, so the claim had absolutely no legal basis. It was just a red herring to try and increase doubt in those people who were too lazy to look it up. It is worth noting, however, that McCain did actually have to deal with the issue. In fact, some people thought he had an even bigger problem given that the Panama Canal Zone where McCain was born was not even considered a US territory in 1936 (McCain’s year of birth). But in 1937, revisions to 8 USC § 1403 were passed retroactively declaring those born in the Canal Zone on or after 26 February 1904 to be citizens (link).
As for the natural-born US citizens and dual citizens you know who have only one US citizen for a parent, there are two possibilities. First, the law changes from time to time. They may have been born at a time when having one parent was itself sufficient. Second, they may have been born to parents who also met whatever residency requirements existed at the time. In 1961, for instance, the requirement was that the parent must have lived in the United States for at least five years after his or her fourteenth birthday. This was the issue raised against Obama, whose mother gave birth prior to her nineteenth birthday. It is possible that the courts would have considered Obama to be natural-born anyway (as the residency requirement may have been interpreted to apply to people living abroad), but it is unclear since no challenge of that sort ever made it all the way through the courts.
@tedd It’s actually quite the other way around. The current laws regarding natural-born citizenship are more lenient than the laws of 1961. Being born on US soil has always been sufficient for being a US citizen. When someone is born outside of the US, however, facts about the parents and/or the place of birth become relevant. If Obama had been born in the Kenya Colony, then his mother would have needed to have been a resident of the United States for 10 years, five of which would have needed to have been after her 14th birthday. As Obama was born when his mother was 18, the residency requirement would not have been met.
This discrepancy is part of why we find such divergent positions as Andrew Malcolm’s claim that Obama’s mother “could have been on Mars when wee Barry emerged and he’d still be American” (this being the claim you paraphrased above, replacing the moon for Mars), and the rival birther claim that his mother’s age at the time of Obama’s birth makes him ineligible. Despite the fact that courts have routinely ruled individual children born to one US citizen to be citizens themselves, birthers point out that the issues in those cases have not been the residency requirement they are attempting to use as the basis of their legal theory.
As it turns out, however, both sides are mistaken. Malcolm is incorrect to assert that merely having one US citizen for a parent is enough (this is false now, and it was false in 1961). The birthers are also incorrect, however, that they have a legitimate claim in need of testing. Here’s what is an open question: whether or not Obama would have been ruled a citizen by a court in 1961 had he been born in the Kenya Colony. This is an open question because the residency requirement has never been tested in a situation where it is the age of the mother causing the issue (or, if it has been tested, I cannot find the case or any report of anyone who has found it).
Here, though, is what is not an open question: whether or not Obama would have been ruled a citizen by a court in 2008 had he been born in the Kenya Colony. When the law was changed in 1986, it was made retroactive to 24 December 1952—which is, of course, almost nine years prior to Obama’s birth. So while the residency requirement certainly is relevant, no one denies that Obama’s mother stayed in the US until at least her 16th birthday. Thus no one can claim that the requirement wasn’t met by the time it became relevant.
For the change to the law, see 8 USC § 1401(g)(B) (link).