Clearly inspired by the Stanley and Livingston story which had been recently portrayed in a Spencer Tracy film, Stanley et Livingstone (1939).
The active map of Popeye travelling across the Atlantic Ocean shows him leaving from Miami. The United States is labeled "US", Europe is labeled "THEM", and Africa is accurately labeled "AFRICA". As he approaches northern Africa, he is fired upon by THEM.
Popeye and Bluto were, as the title suggests, friendly enemies, after all.
WW2 was already raging in Europe; the conflict had spread to Africa as well. At the time of this short, the U.S. had not yet entered the conflict, but the lines were already drawn, as shown here. America would enter the war the following year.