I don't think you'll be able to develop a coherent rule to describe when USAns attach an article and when not. I have a vague recollection of having read a piece* about how German? (I think) usages influenced US English and inserted articles in places British English did not. The "going to hospital" and "going to the hospital" distinction was used as an example. And, because we are rather arbitrary in our absorption of language influences, for whatever reason articles were attached to "hospital" but not to "school," so we still say "I am going to school" rather than "I am going to the school" when discussing the concept in general rather than announcing a specific destination.

Perhaps our German speakers can expand on the use of articles.

Oh - and, Wolverine fans like to refer to their school as the University of Michigan, but that use is more attributable to arrogance than German influences.



*heh. At first, I wrote "an article", but that got too confusing.