Did the lack of Diesel options led GM uncompetitive in overseas markets?

Well it's sure looking quite odd now, but General Motors has wasted many chances it had to offer competitive Diesel engines on world markets. Its former ownership of Detroit Diesel and previous ties with Isuzu and Fiat were not so greatly beneficial to the in-house development of Diesel engines for light-duty vehicles as it would be supposed to do, despite the limited availability of the Duramax 6.6L V8 turbodiesel for full-size trucks. The recent 4-cylinder 2.5L and 2.8L Duramax engines made in Thailand for the Colorado and Trailblazer by the way, are an Italian VM Motori development, and this company is now part of Fiat Chrysler Automobiles. Even though some improvements are done once in a while to the Isuzu-designed Duramax V8 which is now only available for the Chevrolet Silverado/GMC Sierra trucks, and the Italian-designed 4-cyls, the only other significant engine which caters to light-duty vehicles in the present-day GM engines range is the MDE (Medium Diesel Engine) 1.6L formerly available in the US-spec Chevrolet Cruze but now only fitted to the Chevrolet Equinox and GMC Terrain, besides some usage on Opel models which is likely to be phased out soon due to its sale to PSA Peugeot-Citroën. Restricting most of its other Diesel options to Fiat-sourced 1.3L to be fitted only with manual transmissions and catering mostly to India was another mistake, while in other markets throughout the world this very same option had been available only briefly on models such as the Chevrolet Spin and the Brazilian/Russian Chevrolet Cobalt (unrelated to the American one).