Donald Trump says the U.S. needs control of Greenland and the Panama Canal "for national security." Here's why both places are so important.

Many assume this Trump tough talk is his signature bluster, which he uses to threaten allies to do what he wants. When he suggested renaming the Gulf of Mexico the “Gulf of America,” Mexican President Claudia Sheinbaum trolled Trump with a 17th-century map labeling the United States “America Mexicana.”