edit: I should probably add more context as some commenters didn't understand. The DDOS attack is likely coming from compromised IoT devices. Most, if not all, of the big ones in the last few years(decades?) were that. Unless all the devices are located within a specific country and non are within the US then I think it is silly to use that term to imply that this is some sort of war from across the border. The reporting is fine for what they know so far, the submitted title is not.
The overwhelming majority of internet connected devices have an internet connection that's physically connected, for 99.9??% of the distance, with wires or fiber cables, to every other user in the world, with a very nearby wireless hop at the ends. If the cables weren't so fragile, you could pull on your wifi AP and they would see their wifi AP (or maybe nearby cell tower) move.
The tiny fraction of the rest is passed by shining RF transmitters to some distant receiver, separated by some physical distance, to some base station sitting on the ground within a border.
also, “cross-border attack” is a direct quotation from canonical by ars technica, take it up with them