A model has to be less than 10,000 polys in each subobject to fit the .ASE standard. It's not even Alice, it's just an old format. In the case of google warehouse models, they're either 100 different subobjects or 1 very large subobject. Usually the latter. Unfortunately no matter how well organized an average sketch-up user is, they tend to not understand this concept:
It's bad modeling conventions to weld an object if they don't fit the topology already, for example the little box pattern things you see on top of castle walls. They tend to increase poly count far more than necessary—they shouldn't be completely attached to the rest of the wall. I blame this lack of conventions on Sketchup's misleading hiding of edges. If some users actually knew how bad welding objects at random screwed up their model they would probably do it less. So, as the picture says, Welding: Avoid at all costs. That picture was in the sketchup tutorial from a few weeks ago.
At any rate, instead of cutting that castle into different subobjects I recommend you simply get these
castle tiles and make one.
What I meant.