On the other hand, at some institutions one can satisfy the major minimally without a whole lot of courses, leaving plenty of time for non-technical courses.
So to summarize, there is a lot of variability. A US graduate in a technical discipline may have taken anywhere from zero to two years of arts and humanities courses.
For instance, calculus is pretty widely available even if it isn't a diploma requirement.
Parts of the US have world class secondary education and parts don't--just like Europe. Even taken as a whole the US education system ranks higher than many countries in Europe.
>South Korea
The South Korean education system is nothing like the US education system. It's hard to think of a large country more different from the US in this regard.