Other mistake: After the sprinklers go off in the White House, none of the actors' clothes are wet. With the amount of water sprayed, all of them should have their clothes stuck to their bodies. (01:25:00)
Other mistake: Near the end, the sprinklers are turned off in the oval office, which should mean they are all turned off as they all came on together, but where the fist-fighting continues, the sprinklers are still on.
Answer: Knowing is not believing. They might know, but they wouldn't necessarily trust the media. After all it could have been a grand conspiracy to cover up the actual truth from the people.
Alan Keddie
I highly doubt world war 3 would start before these countries did their homework though. It wouldn't take long for them to suss out it was actually terrorists who detonated the bombs and not America.
The_Iceman