It's just as well Team Nutter doesn't really use fertiliser...

Yes, police in rural areas don't have much to respond to a terror attack with. At the same time, the chances of a major terrorist incident in the middle of nowhere are pretty slim as well.

The whole point of a terrorist attack is,well, terror - to hit either as many people as possible or to do damage to some important infrastructure.
It's frankly the polices job to do the risk assessment of those and decide where best to deploy the appropriate assets to provide sufficient cover with the resources they've got.
Blanket arming police officers is one possible solution but it's not one I like the idea off myself. If they know any police they encounter are going to be armed it won't put off a determined terrorist or group - just encourage them to make sure they have equal or superior fire-power.