President-elect Donald Trump has always used his public press conferences and social media posts to seize attention and dictate the terms of national discourse. But his recent trolling about taking over Canada, acquiring Greenland, and reclaiming the Panama Canal reveals something more complex than rhetoric.

These statements, far from harmless social media clickbait, show Trump’s vision for America: a return to the outdated ambitions of domination from the Bush era. For a man who once styled himself as the “pro-peace” candidate, these nation expansion fantasies mark a disturbing pivot...