The Chrysler LX platform was updated for the 2011 model year and is now technically called the LD platform. So it is now 10 model years old. There was some talk of whether they would update the platform again for the 3rd gen cars or switch to the Giorgio platform that underpins the Alfa Romeo Giulia. There was also talk that the Charger would survive for a third generation but the 300 would get the axe.
I'm not surprised that Fiat is pulling out of NA again. It's a niche vehicle in the same segment as Mini, and the brand never really had the cachet that Mini did to begin with. Aside from the Fiat brand, Chrysler was the first to jettison their compact car models, the Chrysler 200 and Dodge Dart. Then Ford announced that most of their sedans were getting the axe, and now finally GM. The automakers can see financial headwinds coming, and they are battening down the hatches.
Asian import sedan sales are slowing down too, but not as much as the domestics. Many people are buying CUVs instead. Most of those don't have a significant fuel economy disadvantage versus the car platforms that they're based on. You're not going to see droves of people trading them in for economy cars if fuel prices spike again, like what happened in the Great Recession. I also read one statistic that consumers often go down one vehicle size when trading from sedan to CUV because they are more space-efficient too, which would also help with fuel economy. (I don't know if that last point is universally true though. last winter I talked with a dealership owner in Vermont who said he didn't think that was the case in his area.)
New vehicle sales are slowing down, and the average age of all vehicles on the road has been creeping upwards. One reason for the slowdown is that the cash-for-clunkers programs distorted the market by pulling ahead future new-vehicle purchases, and many of those vehicles are still on the road. More recently, light truck sales (including CUVs) were also propping-up new vehicle sales, but they've started to slow down as well.
I've read that auto plants need to be running at at least 80% capacity utilization in order to be profitable. Some of GMs plants are running at only 50-60% so they have significant overcapacity. That's why GM is going to the wall with the union now. GM doesn't want to make any concessions which they'll regret if sales continue to fall, and especially if there is another recession. There won't be another automaker bailout next time.
https://www.wardsauto.com/industry/gm-overcapacity-lurks-shadows-uaw-strike
Another concern of GM, which they've stated explicitly, is the promise/threat of electric vehicles. The technology continues to improve while costs come down. Once the economics work out favorably, mass consumer adoption may come relatively swiftly. For comparison, look at the changeover of the rail industry from coal-fired steam to diesel-electric locomotives.