Well, you would know the details of your infrastructure better than I.
I think everyone here would take gross exception to "excellent public transit system", it is far from that, its slow, unreliable, inconvenient and hugely expensive; often cheaper by car unbelievably. In a recent bit of govt and greeny embarrassment, they had to admit that a full Intercity HS125 (125mph) actually causes more pollution than the train-load driving their cars.

We've been forced into small cars from before WWII because of the original hypothetical road tax system that rated cars on the RAC HP rating, this is the thing that throws people across the pond as the Ford CMP manual states it as a 32HP engine whilst you all know it physically makes 90HP.
Pre-war you would pay a pound a year for each HP of rating, a typical trade salary in 1938 would be 200GBP/yr before tax or about 135GBP after taxation, so about 12 pounds a month. So an Austin 7, about as small as you could get, would be around a years salary and nearly a month's pay just to tax, before petrol and insurance.

Not many had cars, and then they were small, only the exceedingly well-off could afford a 32HP Ford or 25HP Morris.

It is also surprising that the typical average annual domestic car mileage between N. America and the UK is very similar at some 12,000 - 15,000 miles. (According to the Canadian AAA)

I think that's a complete fallacy when trucking is involved. Since your mile and hour is the same as ours, then a driver on a 10 hour day averaging 30mph be it in Canada or the UK does 300 miles, that is only halfway up our country. Sure our truckers may make several drops or collections but they commonly do continental European trips too (Poland and back is a fair trip), plus of course they have to obey draconian rules enforced by the hard-copy tachograph in the cab, they are legally speed governed too by hardware, 56mph is the absolute top whack downhill although 51mph is the official limit but they let you have 10% "error". (Annually tested too with all the truck and trailer systems at your expense)
Again, you may be surprised to find the typical UK truck annual average mileage isn't a whole lot different from yours. Diesel oil is a lot more expensive than petrol here too.

Well, according to Transport Canada, some 371,032; leaving out farm trucks, non-cargo/off road and couriers, but including "government" trucks; Statistics Canada reports some 320,000 employed in the Canadian truck industry with 263,000 employed as drivers; presumably one driver drives just one truck.

The UK gov reports 430,000 trucks registered for the UK of 3.5 ton payload and upwards, our "govt trucks" would be military only and not included. Also not included are the British owned, UK operated, but registered in Belgium (Flag of convenience) trucks to minimise the road tax (Vehicle Excise Duty) costs since the UK rate for a semi rig can be anywhere from 1200GBP to some 1800GBP a year; that's $CAN 2,628.96 to $CAN 3,942.44
Don't forget that we have some 60,441,457 people here (24th in world rankings) all wanting well-stocked supermarkets, you only have half that at some 32,805,401 (37th in the world), our people are spread all over the country; yours are more localised with vast expanses of unpopulated wilderness. We already live with more than these prices and have a lower standard of living since a lot has to give for the average Joe just to keep a home, eat and clothe the family.
Our diesel is now just shy of 1GBP/litre or $CAN 2.18897
We now learn our fuel is to rocket further upwards too because of a certain hurricane even more thousands of miles away. Apparently some 8 US refineries are totally destroyed and all US facilities were at 100% capacity meeting the regular demand, therefore there is a shortfall and apparently the US doesn't keep generous reserves as we do. We are to ship refined fuel across the pond therefore and we're told this is upping the price here.

Do you think it will settle back to what it was?

I think not.
Same here.
I guess if we knew that we'd all be billionaires on the futures markets.

R.