The fist must be deployed no matter how much one might personally like  the person giving a comment that is based on questionable (or downright  bad) history, even in the case of President Barack Obama.  In his speech  at West Point outlining the changes in policy Obama intends to  implement regarding the United States and its military presence in  Afghanistan Obama included the following comment:
“For unlike the great powers of old, we have not sought world  domination.  Our union was founded in resistance to oppression. We do  not seek to occupy other nations.  We will not claim another nation’s  resources or target other peoples because their faith or ethnicity is  different from ours.”
I am afraid that the history of the United States simply does not bear  up to this comment when our actions are compared to our peer nations at  any point that I know of in our history as a nation, sadly I am no  expert but from what I do know of United States history and the history  of the various Great Powers in existence and operation during our own  history, the breakdown is roughly as follows:
1781 – 1880s:  The United States expands territory  under its direct political, economic and cultural control through a  policy of continued expansion in a western direction.  These territories  are acquired through a combination of diplomatic efforts and the use of  military force, during this period as a matter of policy the United  States government assumes semi-complete control over the affairs of the  various Native American/American Indian groups residing on territory  later claimed by the United States government.  Key acquisitions include  the Louisiana Purchase from Napoleon I of France in 1803.  Acquisition  of Florida from Spain in exchange for the cancellation of debts owed by  Spain to the United States government/United States government assuming  debt owed by Spain to United States nationals, 1819.  United States  gaining one half (roughly) of disputed Oregon Territory from Great  Britain, 1846.  United States gaining southwestern territories including  California, New Mexico, Arizona, and part of Colorado as war  concessions from the Republic of Mexico, 1848.
In each of the above cases the United States either used military force  or threatened to use military force to gain territory from established,  and diplomatically recognized, nations of equal sovereignty.  (In the  case of Florida the United States had already in the past sent military  forces into the territory and in regards to Louisiana the United States  had already engaged in limited schemes to try and spark revolt in the  territory from earlier Spanish control.)  In addition to this the United  States government through diplomatic pressure and brute military force  either subjugated or expelled native tribal groups from their  long-standing association with certain territories.  Granted the United  States would sign treaties with tribal chiefs or leaders, in some cases  making said leaders up from whole-cloth to validate its actions, but  this is not that different from the techniques used by European Great  Powers in their own territorial gains in Southeast Asia, the Indian  subcontinent, and Africa.
As well the policy of the United States federal government, as well as  that of many state governments during this period was decidedly opposed  to the idea of allowing native tribal religions or social structures to  survive, it was the policy of many levels of government in the United  States to “civilize” native peoples, a war on cultural and religion if  ever there was one.
1880s – 1930s: The United States government engages in  direct colonial/imperial acquisitions of territory including the  annexation of Hawaii in 1900, a sovereign kingdom nation previously  recognized by the United States government as well as other national  governments, as well as the seizure of former colonial possessions held  by Spain after the Spanish-American war of 1898.  These newly gained  territories included Puerto Rico, Guam, Cuba and the Philippines.  Of  these territories the United States still holds Hawaii, Puerto Rico, and  Guam.  The Philippines was not granted full independence until after  World War II and were not granted Commonwealth status until the 1930s.   In fact the United States was gaining these territories at the same time  that the various Great Powers of the world President Obama is probably  speaking of, Great Britain, France, Germany, and Japan, and the United  States was gaining these territories using the same methods employed by  other Great Powers.  The United States also directly intervened in the  internal affairs of many nations in the Caribbean during this same  period, using military force to modify or suppress local rebellions in  many Caribbean republics or dictatorships.  As well the United States  engaged in one of its most brutal and prolonged military campaigns from  1900 through 1904 in the Philippines, suppressing a local uprising that  attempted to militarily defeat the United States through irregular  warfare and establish an independent Philippine republic.
It was not until the 1930s that the United States, under President  Roosevelt, undertook a new direction in its relations with its neighbors  in the Caribbean, the Good Neighbor policy, and renounced the use of  force to defend United States interests in the Caribbean, Central  America, and South America.  However at the same time Great Britain and  France had also begun to reduce their use of military force to intervene  in colonial affairs.  Which makes our policy not exceptional but  instead more of a reflection of the general shift in diplomacy in the  1930s, the recognition by many of the Great Powers of a need to shift  their focus from gaining territory through military force to working  with local populations and leaders to maintain the empires held, a  policy also followed by the United States with our, admittedly, smaller  imperial territorial holdings.
1930s – 1940s: The period of the infamous land grabs by  Germany, Italy, Romania, Hungary, the Soviet Union, and Japan in a bid  to redefine the global balance of power militarily, economically, and  culturally.  The United States did not engage in such antics but, at the  same time the various Great Powers in operation at the time did not  recognize territorial changes through the use of arms.  It may be a fine  point but the territorial shifts of the 1930s were achieved through  diplomacy and consent, the actual seizure of territory by force was,  broadly stated, rejected diplomatically and resisted militarily.  Land  seized by the Soviet Union is an interesting case, it was not actually  seized but instead ideologically loyal puppet states were installed to  rule over the territories in compliance with the policies of the Soviet  Union.
1950s – 1990s: the United States and the Soviet  Union engage in a mutual dance for dominance stretching across a span of  forty years roughly and the globe, known collectively as the Cold War.
  
So overall President Obama your statement does not appear, after  analysis, to truly be accurate against the lens of history.  Unless you  are speaking of quite ancient empires in which case you are correct but  one could also argue the United States had not engaged in such behaviors  of rape, conquest, and devastation such as Rome, the Persians, or the  Huns engaged in because, in large part, we were not on the scene yet as a  nation.