Originally Posted by mineistaken

I understand that. But they would need to know that they were Americans somehow.
They would not ambush random white dudes (if there target victims needed to be specifically Americans).
There would be some kind of target identification process.

I mean you sound like this:
Gacho - we need to kill some Americans to send the message. Lets ambush the first white dudes we spot and kill them. And then hope that they turn out to be American.

I sound like they would at least ask where they are from or demand their ID's during the ambush. If they turned out not to be American just rob them and let them go. Or something. Random white dude killing and hoping they turn out to be American does not sound like a plausible plan.