Trump probably doesn't know the names of very many countries and he had just met with the Norwegian Prime Minister the day before so it was the first country that he could think of. Norwegians aren't really clamoring to emigrate to the United States and every day that Trump is president it becomes less and less of an attractive option.

...otherwise he might take back those F-52 fighters he delivered...

Everyone knows Norwegians are tires of their diets of salt fish and pickled herring and want to come to a land where they can eat a quarter pounder and choose a free market doctor who is benefiting highly from our amazing tax plan. Little Rocket Man will never attack Norway with its vast fleet of American F52s, but everyone there should really come here now. Today.