United States of America
Throughout the 1600s and 1700s, England explored and colonialized eastern North America. These colonies were generally self-governed to begin with, because their existance wasn't too significant to England at the time. These european colonies obtained land through unfair trades with the land's native peoples, and firmly established their rule by suppressing native rebellions. After Europe's Seven Years War, England was left in a terrible debt, and raised taxes among the American colonies. For the taxes, rationale given by the government domestically was that the entire war was ostensibly over their security rather than their protection of their own interests. Additionally, the Proclamation of 1763 England prohibited westward expansion beyond the Appalachian Mountains to appease the natives, who they saw as potentially powerful military allies.
Following English victory in the North American campaign (referred to as the French and Indian War) a wave of British patriotism washed over the American colonists. Several key figures in the later American Revolution wrote home during this period writing in glowing tones about events such as visiting England and getting the chance to meet the King, attend various high society events, et cetera.
In a surprising turn of events, the period of patriotism was short-lived, being replaced by a period of rebellion. As mentioned previously, high taxes were imposed specifically upon the American colonies. Adding to the sense of exploitation: 1) trade barriers were constructed so that goods rare in england were to be sold more cheaply in england and sometimes the colonists were barred outright from trading directly with non-British agents 2) local colonists were required by law to house and quarter troops when army forts were either nonexistent or unavailable to them 3) public speech was slightly curbed.
As part of the government's reaction to recent events such as increased levels of confrontation between colonists and the red coats (American name for the British armed forces) the military presence in larger cities was increased. On March 5, 1770 in Boston, Massachusetts, a large of American colonists attempting to lure a group of red coats into a physical confrontation, began lobbing snowballs at the soldiers and mocking their uniforms. In response to the snowballs as well as a general increase in public agitation the troops were ordered to open fire. The eventual death toll reached only 5 civilians, with a few other injured, however colonial press dubbed the event the Boston Massacre leading the public to fear direct violence from the troops now present in any major city.
Later the Riot Act, though only in place for a short period added to the general public sense of being abused by a foreign government that didn't place a high value on their lives or even allow them to government themselves properly. Events such as the publishing of Common Sense by Thomas Paine and the Boston Massacre led the American public becoming radicalized (by the standards of the day) leading to increased extremes of governmental surpression and recoil.
Requests by the American continential congress to meet with high government officials were either rejected outright or went unanswered. One of these requests came a month before the declaration of independence was signed, warning that insurrection may be imminent, this request went unanswered and (presumably) unread. Finally, on July 2nd 1776, the Declaration of independence was signed and on July 4th the Lee Resolution ratifying it was passed by the continential congress.
The United States obtained independence from England in 1776 in the American Revolutionary War. Thereafter, it gained territory to the west through some more imperialism and genocide. The southern states were generally agricultural states, while the northern states were generally industrial. This lead to slavery becoming a widely-accepted practice in the South, where slaves were necessary to create cheap agricultural products. In the industrial, Protestant north, slavery was generally unnecessary, and came to be seen as somewhat morally unacceptable. Slavery eventually was (mostly) outlawed in the North. Slavery quickly became racially-based, almost all slaves being of African heritage by the 1700s. American slavery was allowed to continue mostly due to a mixture of racism and greed. During the westward expansion of the United States, people considered it important that the power of slave and non-slave states be balanced. Few people wanted to actually end slavery in the South, because it created more wealth for white, male imperialists of the whole United States.
Throughout the early and mid 1800s, an abolitionist movement started. Abolitionists were a group of decent human beings who didn't just want to contain slavery in the South, but stop its expansion, or even actually end it altogether. Abolitionists included escaped slaves who shared their terrible experiences with northerners, and various writers and politicians. Abolitionists generally tried to show the barbarism of slavery, and tried to motivate the people of the north towards ending it. During this same time period, there was a dispute over whether state or federal government should have more power, the southern states strongly supporting state power.
Both the issue of slavery and that of states' rights caused a lot of discord between North and South when Abraham Lincoln was elected president. Lincoln was a big supporter of federal government, and had a moderate, anti-expansionist view on slavery; he also favored high tariffs on British and French goods, while the South hated having to buy goods manufactured in the North. Finally the Southern states seceded from the United States one after one to form the Confederate States of America. Lincoln, wanting to preserve the unity of the United States and the power of the federal government, refused to recognize the states' secessions or let the South peacefully secede. And thus, the American Civil War began in 1861, and lasted through 1865. After the battle of Fort Sumter, four more states would break away from the Union. During the conflict, the cities of Atlanta, Columbia, and others were burned to the ground.
The North won, and the Southern states were placed under a military occupation and forced into a program of reconstruction, where secessionists were kicked out of the southern states' governments, and their government and social structures were rebuilt to meet the needs of the United States. Unfortunately, this didn't do much for African-Americans, who were still treated like shit, and still lived like slaves, for another century.
The United States continued to expand across North America, killing more of the land's native people and moving them to land considered less than valuable economically. By the 1890s, much of the land of the current United States had been explored and conquered.
 Name Controversy
The name of the country "United States of America" is controversial on its own. In its creation, and even today, it reflects a way of thinking that places the country as leader (or even owner) of the rest of the continent. The country has, many times, intervened in other countries of America, especially in South America ("USA's backyard"). As to date, citizens of the US tend to refer to themselves as "Americans" and there is no (unambiguous) word in English to designate those who live in the rest of the continent.
Though controversial by some citizens of other American countries, the name is more of an accident of history. For example, the phrase "the United States have improved their defense capability" was considered grammatically correct for the majority of US history. Until the civil war citizens generally considered themselves citizens of their individual territories with the territories themselves (after the fact) being organized into a larger organization. Following this, a name as generic as "United States of America" was considered acceptable as most of the continent was still colonial and the independent organization was fairly unique for the hemisphere. Mostly dialog pertaining to the name is relatively low (compared to other topics) as the term "American" in this sense has such widespread usage and a widespread understanding that the term is of somewhat defunct grammatical logic.