The first one:
It depends. Average Europeans didn't have a lot of contact with Native Americans, so had to trust secondary sources for their perception of them. These were usually either heavily glorified, or heavily vilified. There was a popular perception of the "Noble Savage" based off of French reports and paintings of the New World, where Natives were viewed as part of nature living in perfect harmony with nature, but lacking the proper tools for civilization. Some British journalists, merchants, and explorers brought back reports of cannibalism and a perception of the uncivilized savage. The Spanish, militantly Catholic, viewed the Indians as heathens ignorant of the teachings of Christ.
Most of the European views of Native people were shaped by their own cultural values and attitudes. Not very many knew about the diversity of the tribes, the vast cultural differences and traits that existed on this side of the world. In a way, Euro-South and North Americans still retain some of these stereotypes and misconceptions. For example, there is a very strong perception in most of North and South America by the non-aboriginal population, that Natives lived in absolute harmony with nature and that the land was 'untouched'. In reality, the Native groups greatly manipulated the landscape of North and South America, and in some cases, drastically altered the landscape.
Second:
The first effect of the Mexican-American War was the territorial gains made by the United States. At the end of the war, Mexico, through the signing of the Treaty of Guadalupe Hidalgo, ceded California (including Alta California) and New Mexico (which including what is now Arizona, Utah, and Nevada) to the United States, and established the Rio Grande as Texas’ southern border once and for all. This secession of land was completed for a final cost of approximately 15 million US dollars (and the U.S. replaced 3 million dollars in claims made against Mexico).
prt 2:
there was the internal dispute of slavery in the U.S. Even before the Treaty of Guadalupe Hidalgo was signed, there had been arguments over what would become of the territories if they were to be annexed into the United States. This was first seen in the Wilmot Proviso. Created by David Wilmot, it stated, “as an express and fundamental condition to the acquisition of any territory from the Republic of Mexico…neither slavery nor involuntary servitude shall ever exist in any part of said territory” (Goldstein 425).