They were streaming the visit live but they weren’t like “here are the exact coordinates where the helicopter will be.”
I also think it’s implied that it would have taken more than just a few minutes’ notice for the Taliban to get in position to even fire the RPG. And they would have had to know the flight path has well. It’s not like they’re all just chilling in the mountains with RPGs waiting for helicopters to fly by. This is why there were a few lines about the president’s schedule. The further he veered off schedule (and Carrie says these missions would be plus/minus 30 seconds), the more time they gave to whomever ended up firing the RPG. For example, if the visit to the base was scheduled for 12 minutes but he ended up staying there for 20, that’s 8 extra minutes they gave for someone to get in position.