The Crown Vics are a rugged vehicle that has been used in fleets for many years and I'm sure both Ford and the maintenance department crews learned a lot about making them work in that application.
Ford also has discounts for fleet sales that probably give them an advantage.
The Crown Vics may be good vehicles.
The Ford Power Stroke diesel trucks I know about had drivetrain problems in manual or automatic, the engine was stronger than the automatic trans or clutch.
The engines dusted at low mileage due to a 'silent recall' problem with the air box. Expensive motors were ruined at 40K due to leaks in the plastic intake/ air filter parts.
The brakes and suspension were high maintenance and usually required complete replacement of all parts rather than an few wear items.
Dodge and Chevy diesel pickups may be a bit better, but they have had their problems as well.
If I had to generalize, I'd say that American cars still leave a lot to be desired in terms of quality, reliability, drivability.
My new 05 Chevy Silverado Crew Cab Duramax started having warranty problems at 300 miles and was towed to the dealer 8 times in 7000 miles before I finally got it fixed.
I had to pull every code from the OnStar diagnostic and demand that the selling dealer's service department escalated to GM's highest tech support team and run down every code and fix the problem not the symptoms.
GM's support and knowledge of the Allison transmission was weak. I like the transmission, but the dealer network was ill prepared, many dealerships in my area don't have mechanics who are trained on Allison.
I want to buy American cars made in American factories...but GM and Ford give me little to choose from or work with.
I'd buy a new Vette or Mustang if I needed one, but I like BMW's more. I can use diesel pickups , and the US companies still have the market, but the vehicles available could be a lot better.
Toyota, Nissan, or Honda could easily give them a run for the money with future models.