In elite schools [edit: that are as elite as] Oxford, the drop out rate would be close to Oxford's. The US numbers are pretty skewed by the massive drop out rate in 2-year community colleges, which both admit huge numbers of people and have very high dropout rates. Also, a huge percentage of dropouts are in the first year, when people are deciding that college may not work for them or be the right fit.
Actually, the US numbers are already filtered to 4-year institutions.
"The overall 6-year graduation rate for first-time, full-time undergraduate students who began seeking a bachelor’s degree at 4-year degree-granting institutions in fall 2012 was 62 percent. That is, by 2018 some 62 percent of students had completed a bachelor’s degree at the same institution where they started in 2012."
(There is some amount of skew based on this definition for students who transferred to a different institution and then completed on time, but it's hard to find numbers on students who transferred from one four-year institution to another, as opposed to all transfers who predominantly come from 2-year community colleges.)
