Do you mean WW1 ? People started migrating through disguise and things like that. Not sure if I’m 100% correct but it’s a starting point
By 1890, the United States had by far the world's most productive economy. American industry produced twice as much as its closest competitor--Britain. But the United States was not a great military or diplomatic power. Its army numbered less than 30,000 troops, and its navy had only about 10,000 seamen. Britain's army was five times the size of its American counterpart, and its navy was ten times bigger. The United States' military was small because the country was situated between two large oceans and was surrounded by weak or friendly nations. It faced no serious military threats and had little interest in asserting military power overseas.<span>
During the late 19th century, the idea that the United States had a special mission to uplift "backward" people around the world also commanded growing support. The mainstream Protestant religious denominations established religion missions in Africa and Asia, including 500 missions in China by 1890.</span>
The population of Mexico is Approximately 126.2 million as of 2018
My best bet would be B. the US and spain both had control over economic trade and stuff.
