I'm surprised no one else has made the connection. In person it looks very similar to the 300, and that's because they're both on the same LX platform, with the Ghibli getting fancier suspension. Even its turbo V6 engines are based off of the Pentastar V6, being cast at a Chrysler plant in NA, then flown to Italy to be assembled.
Even the interior is the same, the Dashboard has the same layout, including the vents, HVAC controls, gauge cluster, and touchscreen.
Having sat in the Ghibli, it felt very familiar to me, I then realized that it was because I had rented a 300 for a month a while back. It had nicer leather sure, but all the plastics were of the same quality, and honestly you shouldn't go into a Maserati and be reminded of a Chrysler that costs $50,000 less.
The performance of the Ghibli also leaves a lot to be desired compared to the competition. A Lexus GS350 F Sport will match a base Ghibli off the line with a 45HP disadvantage. The BMW 550i, Audi S6/S7, and Mercedes E550 also beat the Ghibli Q4 in performance.
I'm sure the average Maserati owner will never sit in a 300, but for those that have the familiarities are noticeable and disappointing in a car that can be priced past $100,000.