The US government is only the longest continuous democracy only if one believes that the US is still a democracy. I've read some decent arguments that the US stopped being a democracy with the McKinley administration, and others that the US ceased to be a functional democracy during the Second World War. In both cases, the claim was that the USA became an imperial oligarchy.

It is questionable whether any democracy truly exists at this point as I've seen no nation where the will of the people is typically manifested in the actions of the state.