I noted in the post on Kate Middleton's family tree that the English are pretty much all related to each other. And of course the colonies which became the USA were English projects.
Every single US President bar one (Martin Van Buren) is a descendant of King John I of England.
Including Obama (who's also descended from (inter alia) King Edward I (Longshanks) of England, King Henry III of England, King Henry II of England, King Henry I of England, King William I (the Bastard) of England, Count Baldwin of Flanders and his daughter Matilda, King Robert Capet I of France, King Louis I of France, and Charlemagne). Obama also shares a common descent through Richard Eltonhead with Queen Elizabeth of Great Britain.
Not to mention apparently being descended, along with George Washington, from Halfdan The Old and through him from the Norse god Odin.