It is not related to who founded the system, it is the base of the ISO system. And this is used almost anywhere in the world, not only all over Europe, also in most of the countrys of Africa, in China and Japan and South America. The US has a population of about 250 million people, the EU about 540 million, China about 1.2 billion, India about the same. They also changed from the british system to ISO.
Is the US not flexible enough to learn the system?
I do not want to start a basic discussion about measurement systems.
However, all customers I have in the US they all work in the metric and ISO systems. They had to learn it the hard way for it is the only way to compete on the world market.
The US Army these days also uses the metric system. It makes sence in the nowadays world. Look at the rear of the manuales, they contain conversion tables to make the soldiers fit for the metric system.
Mack is still owned by Renault. You mix it up with Volvo White/GM trucks. Renault is these days owned by Volvo, however, that makes no differance for Mack.
Frightliner is owned by Daimler, as well as Western Star, Tomas built busses, Sterling (dying soon) and Detroit Diesel-Allison.
The DD15 Detroit Diesel engine is a Daimler engine. Before the D50, D55, D60 engine series were also Daimler engines, based on the OM 457 engine series, of course all metric!
The 6.2 l Diesel as well as the 6.5 l Diesel used by GM is a Detroit Diesel engine with blocks and heads casted in Germany. These engines are full metric. The Avalange Diesel is a Isuzu Diesel and also metric.
Wolf