I drove a 99 Cougar for 10 years. Ya I know, chick car, get over it, but it was great for my needs at the time, and the design literally changed the shape of what other car companies were doing. Very avant garde in it's day, and they still look contemporary compared to much newer cars.
Designed in Germany, developed in Belgium, and shared the exact drivetrain as the Mondeo and Contour. Which was Ford's first "world car." The chassis was designed by Ford UK, the structure was designed by the German division, and the V6 started life as a Porsche design that Ford bought and had Cosworth re-engineer.
It was built in the same Indiana plant as the 626 and Probe, which later started turning out the previous generation Mazda6, and now spits out Mustangs (which have some Mazda technology in them, btw).
Anyway, the Cougar was literally a Mondeo coupe. Except for some brake and suspension changes, exactly the same car under the skin down to the millimeter.
And what a POS it turned out to be. It had no Mazda or Volvo engineering, it was just built in the same Ford/Mazda Indiana plant, Auto Alliance, and the euro version was shipped overseas.
I could fill a page with all the problems I had with it over 85K. The big items were a failed hood latch that nearly killed me, and a total brake failure. That was when it was under warranty. After several quiet years other systems started giving out, like the complicated intake manifold design (twice), all 3 cats went south at about 60K, the A/C compressor (twice) and many, many other things broke along the way while the paint decomposed.
In the end, I only got $600 for it on trade for my 2009 MS3. I maintained it by the book but you can't really maintain a car that was s*** to begin with, you're just constantly fixing things and getting the oil changed as long as it's on a lift getting an expensive part fixed. Global Ford engineering, Mazda/Ford assembly, Fiat reliability. The mechanically identical Contour was a much more reliable car.
Why? Parts sourcing and point of assembly, which differed. All car companies use suppliers and their quality can range quite a bit even if they're supposed to be built to the same design standards.
Many of the parts in the MS3 have "FoMoCo" stamped onto them, but that doesn't mean that Ford actually made them, they were most likely outsourced from any given point in the world. They just screwed the pooch on the Cougar, and dropped it after 4 years. A Mazda6 was on my short list of car choices, but when I learned that it was built at the same plant I changed my mind and got an MS3. Yes, the C1 platform was a joint Ford/Volvo/Mazda venture, but I'm approaching one year without a single manufacturing problem, recall, or warranty visit.
Reason? I can't be sure, but I suspect that since the MZ3 and MS3 were developed and built by Mazda in Japan probably has something to do with it. Not that Ford can't make a good car on their own - many of their products are rock solid - but the lack of "Fordness" and Japanese assembly factored into my thinking.
So far, so good. Significant engine mods are known to blow motors, but it already has enough power for a FWD car, so I've only made improvements to the suspension and love it. 3's are very very popular in my part of the country, and informal surveys by me suggest that it's a very reliable car. Having the last production run probably helps too, its 6 years younger than this thread is!
The Mazda6? Eh, not so much. Mazda tweaked Taurus engine and Indiana assembly might have something to do with that, but I know a few owners who've had several problems. Mustangs too, I think that plant is pretty much a lemon factory.