How did Columbus's voyage negatively affect America?

Christopher Columbus's voyage led to subsequent European contact with the Americas, which had many negative effects. One of the most immediate effects was bringing diseases such as smallpox to which the native inhabitants had not developed immunity. Some scholars estimate that up to ninety percent of certain native populations in the Americas may have died due to diseases such as measles and smallpox brought by Europeans.
Next, many Europeans arrived as conquerors and colonists, taking away land from indigenous people, impoverishing them, and disrupting their local traditions. What had once been wealthy societies became impoverished and oppressed, and even today, many indigenous people live in poverty and have shorter life expectancy than the descendants of European immigrants. Many European settlers claimed the best farmland, evicting native owners.
Another major negative effect was environmental. Native American populations practiced sustainable lifestyles, while settlers exploited the environment for short-term gain. The passenger pigeon became extinct, and many previously plentiful species such as bison and wolves were threatened with extinction.
http://www.pbs.org/gunsgermssteel/variables/smallpox.html