Most places do not have fiber.
There's a long way to go before fibre is commonplace across the world.
You cant just assume everyone is talking about your country online.
I get being too US-centric, but I think it's interesting if the US has the right combination of hosting tons of infected devices and having the bandwidth to use them on a much larger scale compared to other countries and possible implications.
>DDoS Botnet Aisuru Blankets US ISPs in Record DDoS