To me, the language is plain. Adding the authors thoughts behind those plain words removes any interpretation. As others have said, it would have been simply inconceivable to these men that this country would sit idly by while being invaded by the millions. Therefore putting too fine a point on the issue somewhat silly.
The "wall" is another issue entirely. Not referenced in the constitution, only in one man's correspondence to another. When one researches the circumstances surrounding the letter, and reads the original unedited letter. The "intent" of the phrase becomes likewise quite clear.
More here:
http://www.usconstitution.net/jeffwall.html
So sometimes you follow the language, sometimes you follow intent?
I know you think the language is plain in the 14th, but I think it's plain too, and I draw the opposite conclusion from yours.