It may be worse than that. I bet a lot of these ridiculous announcements are not serious, but just a way to desensitize public opinion so that it will become numb and apathetic and not react indignantly to other outrageous maneuvers in the future. For example, Trump may never actually threaten to buy Greenland from Denmark, or turn Canada into the Maple Leaf State, or invade Panama, but he may have other shakedowns under consideration for those countries that won’t come across quite as brutal when compared with these proposals. For example, he may not necessarily annex Canada, but he may force them to do something he wants (and they don’t) without causing too much concern. In international relations, a threat is often as effective as an injury.

Or he may use these threats to force Panama to give up lucrative trade or development deals with other countries if Panama doesn’t give the USA special rights and privileges on the Canal. Americans will shrug it off as routine diplomacy since no actual invasion will ever be attempted (as long as Panama cooperates).