His mother was indeed a US citizen. His father, however, was a foreign national...British.
This is established fact, as is also the fact that not being born from parents who were both US citizens automatically disqualifies Obama, per the Constitution.
Why is this so hard to understand?
They don’t want to understand it.
Fingers in their ears, heads in the sand, thumbs up their asses.
One or all of these may apply.
The truth hurts their belief system, so they would rather play dumb.
Technically, that's not correct. His presumed father was a British national, but without the original source document, we do not know for certain if Barack Obama, Sr. is indeed the father of record.