There are 3 city states in the world. They are linked together, as the ‘Empire of the City’. The Wash DC flag has 3 stars on it, purportedly for these 3 cities.
Washington DC.
City of London.
The Vatican.
No, not even close.
The arms of Washington, District of Columbia are derived from the personal arms of George Washington, which date to 1592 or earlier.
https://en.wikipedia.org/wiki/Coat_of_arms_of_the_Washington_family
The are plenty of city-states in the world, but you definition is faulty.
The City of London, is a unique local government area in Greater London created under British law
Washington, DC is a federal district under US law, administered by a government created by the Congress
The Vatican City state is an independent state created by a treaty with Italy.
Of course under this loose definition you are using, Singapore, Moscow, St. Petersburg, Hamburg, St.Louis, San Francisco, and every city in Virginia all qualify as “City States”.