Donald Trump really loves the idea of American expansion. During his first term as president, he looked into whether the U.S. could buy Greenland from Denmark. During this year’s presidential campaign, he vowed to colonize Mars. He and his aides and allies have repeatedly flirted with the idea of invading Mexico. More recently, he’s suggested Canada should become the 51st state. And as of this weekend, the trade-warring president-elect is now threatening to seize the Panama Canal.