What do you think yamamoto's biggest problems were in building the japanese empire in the pacific?

Thinking the Americans were lazy and fearful, and that the Japanese were invincible

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.

i do not know if this question has options, but a main impact of the federal reserve act of 1913, which created the federal reserve bank, was the international use of the u.s. dollar, which soon became the world's leading currency - particularly during world war i, since many nations around the world asked the united states for money.