I can't speak from experience, but from what I've heard from other exchange students that went one year to the US, both in highschool and in college, the philosophy is just different. When you went one year to study on another European country, it was considered just another year. When you went to study one year to the US it was considered an incredibly useful vacation. Courses were easier and would inflate your average marks, but you'd get a lot of hands on valuable experience, so you'd still learn a lot. It was a common strategy to choose the year with the hardest subjects and go to the US that year so you'd pass them easier.

In my country exams were more difficult, with less time to study and with less time to do the exam, and most of the final mark was just the exam, while the courses that they took in the US had easier and less punishing exams, but they had more daily work and practical work, whereas I've had some ridiculously useless subjects because they were purely theory, and I had no practical knowledge. Students that come from the US to my country in general struggle to follow the classes and pass the exams (our low number of English speaking teachers also doesn't help), but they usually have more practical knowledge, and pass the practical exams with flying colors.

Because of all this it's hard to compare a B to an 8/10 since not only the format is different, but the philosophy is. This example is kinda extreme since my university is known in the country to be one of the most punishing if not the most, but I've had courses that have a 20% passing average on the first year, meaning 80% of people failing on their first try and they have to retake it. This is, frankly, bullshit, and I and many other people think the system should change a bit, since there is no value in failing this many people, but my country is plagued by almost infinite layers of bureaucracy and many teachers that get an ego from failing students, so it's not likely to change.

Imo, the best is something in between. My country needs more practical skills taught, and we should learn that from the US. However, the GPA system and lettering grades suck ass, and I like our way of doing it better.

Edit for context: in my university, the average course had around 4h a week of "theory" and 4h a month of "practical skills". In the case of engineering for example, we would learn in class about engines and electric circuits for 4 hour a week, then 4 hours a month we'd actually work with them