So Fargo.

Why does the cop have a Canadian accent? Are pre-'98 Crown Victorias really still in service anywhere anymore?! Why would there be a traffic light on a rural road in the middle of nowhere? Wouldn't be worth the expense.

Dave, as seldom as I've been in North Dakota that don't sound like no Canadian accent to me.

"Why does the cop have a Canadian accent?" - I lived by the North Dakota border with Minnesota for the better part of a decade. Believe you me, dat's pretty dern close to being authentic der den.

As for the other two questions - Yes, the more sparsely-populated areas of the North Central US often do have older law enforcement vehicles, as there's a lot less revenue to work with than in your more urbanized areas. And for the traffic light, it's obviously a pork barrel project passed thanks to one of the state's aging Senators.

Shouldn't you be more upset about the frozen guy? Why didn't he use the heater to compensate for the convertible top being down? Why is he wearing that light shirt in the wintertime? Shouldn't he have put the convertible top back up when it started to get cold? Why didn't he have the car stereo going? Shouldn't he have been wearing thermal underwear?

It's a commercial. They had some fun. Stop clenching those hinder cheeks of yours so tight, 'k?

I know, but seeing as its a Ford ad, wouldn't Ford be wanting to also take the opportunity to show off its new Crown Vics, rather than old rusty ones?
Here in Australia it is unusual to see any police, taxi etc. vehicle older than 5 years. They quickly retire them from service once they reach a certain age/mileage and thats usually about 4-6 years. A '97 Crown Vic (or earlier) would now be well over 8 years old.