One of the more famous assassinations in history started World War I and (surprise, Col!) the assassin wasn't from the USA. I know you won't believe it, but we don't own the franchise on assassinations or attempts thereof.
Actually, several events led up to that moment. Archduke Ferdinand was visiting Bosnia at the time and was killed. The archduke was visiting Bosnia because of the recent annexation of Bosnia and Herzegovina, and a Bosnian student named Gavrilo Princip actually did the deed, though there was a conspiracy among at least six people engaging in political activism.
Other outside-the-USA killings of people for political purposes...
Jamal Khashoggi - internationally prominent journalist killed in Istanbul, presumably because he was anti-Saudi-royal-family
Tsar Alexander II of Russia (by a revolutionary group)
Empress Elisabeth of the Austrian/Hungarian empire (by an Italian group)
Giacomo Matteotti of Italy (by Mussolini's allies)
Mahatma Ghandi of India (by Sikh forces)
Indira Ghandi of India (was Prime Minister at the time; by Sikh forces)
Benazir Bhutto of Pakistan (took two tries to get him)
Aldo Moro of Italy (was Prime Minister at the time)
And how can we forget Julius Caesar, killed by his own senate and his friend Brutus?
That is enough of a list to show that the USA isn't unique in the world when it comes to political killings.