Some U.K. universities are moving from the system of lecturer->senior lecturer->reader->professor to the American system of assistant professor->associate professor->full professor. However I don't think this is going to reduce the confusion abroad regarding the U.K. system. AFAICS in the US, most academics that stay in academia end up as full professors, where as most academics in the U.K. are never promoted to professor (it is more equivalent to an endowed or named chair in the US?). From my minimal research I'd estimate that in the US ~2/3 end up as full professor but only perhaps ~1/3 in the U.K.
This means in the U.K. there are quite a lot of older (50s/60s) academics that are senior lecturers and likely to remain that way until they retire. How are associate professors in their 50s and 60s viewed in the US system? Are they viewed, if not as "failures", then as "unsuccessful" or "second rate"?
Asking for a friend ;o)