Why did the US suddenly come up with this video now, several months after the incident?

There's probably a huge backlog. Have you any idea how many terabytes of data spysats generate? I wouldn't be surprised that at the time no one in the Pentagon thought a spysat would have recorded this event as it unfolded. I know I didn't. Obviously you didn't.

It would have been very useful right after the shooting.

But I'm sure someone else would have said "Why did the US suddenly come up with this video now.....The US military is well known for it's ability to lie....."

And why did they coincidently happen to be filming that checkpoint via satellite recording?

Maybe it was coincidence. It happens. Or maybe Pentagon officials like to keep classified just how much ground activity their satellites do in fact record.

The US military is well known for it's ability to lie. It's called counter-intellegence.

Are you saying this satellite evidence is fabricated?

However the term Intellegence is rather a misnomer after 911.

Please don't berate intelligence failures when you can't even spell it.