Looking at the BA requirements in the states it seems undergraduate education is slimmer than the requirements here. This is the courses I took within my philosophy degree and it seems we take far more credits than what colleges demand (I'm excluding philosophy courses I took that were a part of my LLB requirements). I wonder if American courses are just chunkier and have a thicker syllabus.
This is generally true for all US majors of substance compared to developed nations. Our first 2 years of college are basically high school (and increasingly so), and you dont really get into non-basic major courses until your junior year. In the sciences, a phd in Europe dives straight into research, while most of our schools need a year of courses first. The more mathematical the subject, the further behind the US is.
On the other hand, we still get the best students from around the world, so we still lead research-wise.