Externality? Who do you think is bringing you food and all the items you buy? Even locally?

The Grenadier Guard?

Currently the complete cost of shipping food includes road damage that is not priced into shipping but instead borne by all citizens. By making those responsible for road damage, pay for it, they have an economic incentive to stop the damage.

Not priced into shipping, but equally borne by all tax payers. If all tax payers benefit through transportation of food and other essentials, that’s not really an externality? The people paying are the ones who benefit?

It's an externality because the people who are paying aren't the people who are causing the damage.

This isn't so much unfair, but it does remove incentives for the shippers to cause less damage to the roads.

A truck damaging the road dis-proportionally is an economic externality [1].

[1] https://en.wikipedia.org/wiki/Externality