Why? He's an American citizen. Nobody disputes that. Why did they have to go out of their way to try and give him a something he already "presumably" has? (We know why they ignored Obama). But why McCain? Why?
Didn’t follow the issue, and I don’t try to explain acts of Congress. I can surmise politics was involved. Was it a bill? A resolution? Who introduced it? Who sponsored it? Who voted for it?
Because laws are sometimes complex and/ or misunderstood by the public, and therefore Congress sometimes passes a law to clarify what the law actually is.
It's exactly what our Senators and Representatives did when they passed the Civil Rights Act of 1866, and declared that black people born in the United States were US citizens.
The sponsors generally said that the law was simply a declaration of what they already understood the law to be. It just needed to be clarified, so that no one could deny it.
Actually, people did dispute that. Most notably, a University of California professor wrote a paper arguing that "because Senator John McCain was not a citizen at birth, he is not a nnatural born Citizen' and thus is not 'eligible to the Office of President' under the Constitution."
It wasn't a bill, anyway, it was just a resolution "recognizing that John Sidney McCain, III, is a natural born citizen." In other words, they weren't claiming that the "bill" made him eligible, merely that they were recognizing his eligibility.