Fiat Chrysler Automobiles NV and Peugeot-maker PSA Group cemented their trans-Atlantic merger Saturday, creating Stellantis NV, a global auto-making giant that executives say will have the heft needed to compete in a fast-changing industry. snip---- Stellantis will have a major presence in North America and more than a quarter of the market in Europe, selling vehicles through a massive collection of brands, ranging from American names like Jeep and Ram to Peugeot, Citroën and Opel in Europe and Maserati and Alfa Romeo on the luxury end. snip---- Carlos Tavares, the PSA chief now leading Stellantis, faces numerous challenges in fitting...