I think if you elaborate on your question and what exactly you're looking for you might get a better answer. Since the United States government is still very much active and functioning, I don't know if you are asking if it was toppled in the past but was rebuilt? The only argument I can really see being made is that the United States government was "toppled" during the Civil War due to the union being split in two, but even then the United States government was still very much alive in the North.