It happened and it was not in trading hours. That are the facts.
So your IF has no importance as you can never know with 100% certainty that it will or will not have an impact. So you are just guessing. You don't know what the effect would have been. It would not be the first time that the market would react opposite to what everybody was expecting. If you could predict what the market would do you would be billionaire.
After 30+ years in these markets, I can say with certainty that the impact of such news would have had serious affects on all the markets during trading hours. As far as the magnitude of such swings that would be an unknown. If you would like to test this, just go back to the desert storm day when the news first hit the markets that day. Fortunately for me that day I was just watching the price action when that event took place. But, I'm sure you might just say that was an invasion. But an Emergency warning from Hawaii, about incoming missiles? If you think this is not a market moving event than you are gravely mistaken.