In this video segment, from the PBS documentary Looking for Lincoln<span>, Henry Louis Gates, Jr. and historian David Blight examine President Abraham Lincoln’s mixed motivations for issuing the Emancipation Proclamation. They conclude that while Lincoln ultimately recognized the moral righteousness freeing the slaves, his first and primary concern was strategic: it was the best way to rally the North and strike at the heart of the South’s economy. Gates and Blight then join a roundtable discussion of Lincoln scholars debating the legal authority of the Proclamation and its special meaning for African Americans.</span>
USA had a better navy. (The White Fleet?)
USA was backed by guerrlia warfare in the Philippines.
USA had terrible guns going against the Spanish in the San Juan hill.
The USA Springfield Gun 1892 - 99 side clip was highly inefficient compared to the Spanish Mauser.
The Spanish had more firepower the Maxim beat the Gattling Gun.
Answer:
California's size and distance from Mexico
The completion of transcontinental railroads in the United States and Canada