Trade was the motivating factor. The silk road accross Asia was besieged by bandits & required bribes to a number of nations to transport goods to & from Asia. Therefore a sea route would be a much safer & less expensive means of getting trade goods to & from Asia.
People thought that an alien invasion was happening
Both had major rivers and dependable flood
Hey there!
There are a few different territories that were gained by the Mexican-American war. The Treaty of Guadalupe Hidalgo granted the Mexican cession to the U.S. If by territories you mean states, the Mexican Cession included parts of states including California, Nevada, Utah, Arizona, New Mexico, and Wyoming. When Texas was completely annexed, it gave the U.S. all of Texas and parts of New Mexico, Oklahoma, and Kansas. The Gadsden Purchase also gave the U.S. parts of Southern Arizona and New Mexico including cities such as Tucson.
I hope this helps!