That's not really what anyone is talking about here. We're talking about if a USB cable itself could be an issue. For that to happen the cable would have to be shorted in a way that still coerced a USB upstream port to still deliver 2A. Even long and bad cables are going to have incredibly small resistances compared to any piece of electronics they're attached to that can make the USB port think that's okay. Which means that the majority of the energy dissipated in a USB short will likely be in the downstream electronics. You could probably use something besides copper and still have it be the minority of the resistance in a circuit that could get 2A.

If a USB device gets more current than it's supposed to get, it difficult not to blame the upstream power port for providing so much under the conditions of a short or the downstream port for not being designed correctly. Furthermore, when people see USB cables with "only 2 strands of wire" these are power cables where the data pins are shorted with a resistor, which locks a USB port to a more modest 500mA. That's definitely fine.

In fact, ohmic (i.e. reistance-based) heating is entirely independent of voltage; it depends only on amperage. Higher voltage is only dangerous inasmuch as it may increase the amperage.