It's unclear how the issue of ownership of the Panama Canal became a talking point for President-elect Donald Trump this week, but the question has a long political history.

President-elect Donald Trump spent Christmas Day laying out his foreign policy aspirations for his second term, including his threat to retake control of the Panama Canal. He also suggested the U.S. could take control of Greenland and Canada.

President-elect Donald Trump has once again repeated his desires for U.S. territorial expansion. In a message delivered on Christmas Day, Trump took aim at the Panama Canal and Greenland, while also addressing Canadian Prime Minister Justin Trudeau directly.