<span>This is of course somewhat of a subjective question, but in general most would agree that in general expansion was not justifiable since the Mexicans and Natives were doing nothing to provoke the US. One could argue it was justifiable since Americans needed more land. </span>
Explanation:
Indian Treaties and the Removal Act of 1830
The U.S. Government used treaties as one means to displace Indians from their tribal lands, a mechanism that was strengthened with the Removal Act of 1830. In cases where this failed, the government sometimes violated both treaties and Supreme Court rulings to facilitate the spread of European Americans westward across the continent.
Andrew Jackson
As the 19th century began, land-hungry Americans poured into the backcountry of the coastal South and began moving toward and into what would later become the states of Alabama and Mississippi. Since Indian tribes living there appeared to be the main obstacle to westward expansion, white settlers petitioned the federal government to remove them. Although Presidents Thomas Jefferson and James Monroe argued that the Indian tribes in the Southeast should exchange their land for lands west of the Mississippi River, they did not take steps to make this happen. Indeed, the first major transfer of land occurred only as the result of war.
Prior to the Industrial Revolution, which began in Britain in the late 1700s, manufacturing was often done in people's homes, using hand tools or basic machines. Industrializationmarked a shift to powered, special-purpose machinery, factories and mass production.
Spain closed the lower Mississippi River to American trade because if American relations with Great Britain were poor, affairs with Spain were worse. Spain, which held Florida as well as lands west of the Mississippi River, was anxious to halt American expansion into the territory it claimed. As a result, Spain closed the lower Mississippi River to American shipping in 1784.
First amendment freedom of speech and religion, 4th the right to be secure in their persons houses papers and documents, and 19th gave women the right to vote