MULTIPLE CITIEIS ON THE SAME DAY. IE The Spanish 3/11 was MONTHS after 9/11. It's unlikely they would carry out attacks on multiple continents on the same day, namely because their cells are regional, and there is little lateral communication.
Okay, now I get the jest of your post.
I thought you meant multiple attacks on a particular day, i.e. several subway stations and buses attacked.
...and they all work at the local 7/11. Keep your head down next Monday.
They don't need orders from above or lateral communication, unfortunately. All some US cell needs to do is see this on the news, and decide autonomously that today is the day, in order to capitalize on world chaos.