What I know is limited, and this is for an arts program...
It is my understanding that 1 year is spent in foundation studies as one seeks out their intended course of study, or major. 3 years are then spent studying in the major, rather than the 2 undeclared years in the US, followed by 2 years of study in your major.
Therefore, my University credits from the USA (even liberal arts) are not applicable. My adviser in London said that he feels I am focused enough to skip the foundation year, which my American adviser says is atypical for foreign students.
Therefore, credits are not transferable. I also think it has something to do with the UK's education system being a bit more difficult in secondary schools, with courses at high school level which are more typical of undeclared work in the US.
Please note that this is for
art school. Many of my credits from my old traditional university would not have worked at a US art school either. I am 4th year (I found out I hated my old major-to-be), so it is a bit sad. But I am more prepared to live alone overseas now than when I graduated from high school, so everything happens for a reason!