1846-1848
Yes. it went to War with Mexico.
Mexico
It is called the Mexican American war for a reason. The US fought Mexico.
From 1846 to 1848 in the Mexican American War.
Only one, the Mexican-American War (1846 - 1848).
Mexico was part of the Allies and about 15,000 of them joined the US military and mainly fighted sgainst Germany or Japan.
Because although President Polk sold this war to the congress and the American people as a "fight for our sovereignty", in reality it was a war of aggression with the intent of stealing California from Mexico. Therefore, it was natural to fight this war on Mexico's territory. See related questions for further details.
In the Zimmermann Telegram, Germany tried to convince Mexico to start a war with the US, which would prevent the US from joining the Allies during World War I. In return, the Germans promised to send Mexico money and supplies to help fight their war. Additionally, Germany promised that if they won the war, Mexico would be allowed to take back Texas and California, which the US had taken from Mexico about 60 years earlier.
No. Mexico has never attacked Cuba, and the US has only used covert operations against such country, but never outright war.
texas, California, Nevada
Mexico gave support to the Republicans including weapons. The US was officially neutral, but at least two thousand US citizens served in the International Brigades against the Fascists.
Texas.