I wish there were some sonics around here. The nearest is many miles away.
I think you should continue with the sonics category. There seems to be a misunderstanding about global versus non-global. What it really means in waymarking is that a category should not be written to explicitly exclude places outside of its usual area. For examples:
1. Sonic Restaurants - it is OK to have the category be Sonic Restaurants even though perhaps all Sonic Restaurants are only in the U.S. and perhaps never be anywhere else. On the other hand it would be non-global to have the category title be: Sonic Restaurants in the U.S. or Sonic Restaurants in Arizona, or for the title to be just Sonic Restaurants but the waymarking criteria say that only those in the U.S. will be accepted.
2. U.S. Post Offices - it is OK to have a category be U.S. Post Offices but not U.S. Post Offices in the U.S. There could be (as far as waymarking is concerned) a U.S. Post Office in Antartica, France, Indonesia, or anywhere else.
The global-only idea is excellent but not as simple as it first seems.
It is unfortunate that some people misunderstand the global idea and vote against particular categories because of this misunderstanding.