Well first thing is you need a little help from a real lawyer who knows how to do real legal research and he needs to do it either in a real Law Library or have access to one of the more complete research engines.
You need to get back to the provisions of the United States Code in 1961 where you find that provision. You then need to see the modifications which tell you that the modifications apply only to people who are born after the effective date specified for the modifications.
To do all that you also need the footnotes in the Annotated code or you need to get to the actual enrolled legislation where you find the effective date clauses.
Not really easy to do but real lawyers can show you how to do this stuff.
My answer to your proposition about the "mexican" is above.
tTat is really funny. Thanks for that. The mystical 1961 statute over riding the Unites States Constitution. You are kiddig, right? Tell you what ,lawyer, give me the statutory citation on that big news.