Yesterday, President Trump made his first address at the United Nations (an organisation he's brushed off as a "club" for people to "have a good time"). During his speech to African leaders, he praised "Nambia" for its health system, even though that country doesn't exist. He actually mentioned the fictional nation a couple times during his remarks.
It's possible that the gaffe was a mispronunciation of Namibia, Zambia, or Gambia, all of which are real African nations, but that didn't matter to Twitter. The internet sounded off right away.