Question

The zimmerman note outraged americans by proposing that _________ join germany in a war against the united states.

Answer 1

The zimmerman note outraged americans by proposing that _Mexico_ join germany in a war against the united states.

Answer 2

I believe the answer is Mexico
The Zimmerman note was a diplomatic effort between Germany and Mexico during the World War I.
German felt threatened if United states join the opposition, so the notes tried to persuade Mexico in joining German's central power in case the United States decided to come into the war.