@2SpiritCherokeePrincess
A few points here:
A) American Indians (which is the correct term as "Native American" is primarily associated with the nativist party, not the indigenous peoples of precolonial America) still have sovereignty in certain parts of the nation. Granted, not all the tribes or customs have territory, but it is true that the American Indians still have their own jurisdiction and governance.
B) What happened to the Native Americans was not genocide. What wiped out most of the Native population was disease, which would have happened regardless due to the lack of beasts of burden within the Americas and so any contact from any culture would have lead to most native populations being wiped out. The American Indian population at the time was minuscule, and was nothing compared to something that we do not consider a genocide such as Caesar's invasion of Gaul which had more tribes killed in single battles than the total of most conflicts between American Indians and European settlers. Most of the worst deeds were committed before America was founded, such as by the British and especially the Spanish, and not the American government itself. This is not to say that America didn't have its share of atrocities committed against the native peoples, such that is evident through the Battle of Wounded Knee, Indian Removal Acts, and Trail of Tears, but when compared to the systematic subjugation, extermination, and enslavement by the Spanish, and the various crimes committed under the British Government, the US is a far less egregious offender than its peers. You must always grade on a curve when looking back onto the past. Every nation has blood on its hands, the drive to expand, and crimes by which you can look at them with discontent, but America has tended to be able to acknowledge its mistakes but amend them.
Besides, it does not help that Native populations themselves varied on their customs and views and different tribes were more or less "imperialistic" as others. Tecumseh wanted to unite all of the tribes on his half of the Mississippi River, willing or not, under his banner to oppose the Americans. The Iroquois, perhaps the most socially advanced of all the North Americans, still had periods where the Five Tribes would expand its borders. Do not even get me started on the Aztecs, Inca or other Mesoamerican powerhouses which were known for their tributary empires and labor taxes. The Aztecs had the "Flower Wars" which they used to enslave other tribes for the sole purpose of sacrifices. Cortes could not have defeated the Aztecs if he had not convinced the other native tribes to rebel against them first. Compared to the US which acquired most of its land through purchasing them via treaties, diplomacy, and negotiations, the Empires of old and the contemporary times were far, far worst and more oppressive. (Also, aside from Texas, which was its sovereign state because of its rebellion from Mexico, the US legally acquired its land. For all legislative purposes, what it did was not "stealing" land, because it rightfully either bought it, earned their independence from other nations, etc. Only a very small percentage of land was fought over with Native tribes due to the fact the US had the power to either buy them out, set up treaties do to the differences in manpower and technology, or just integrate the tribes into the US naturally through cultural osmosis. The Native Americans didn't have any power to enforce a claim to the land because to a large majority of the tribes, no one COULD own the land. It wasn't THEIR LAND, it was just a part of nature. It was also too scarcely populated to hold because of disease, and so it would inevitable that someone would fill the power vacuum and take it eventually.
You may decry it as unfair, and you would be right, but it was nothing exceptional not only for its time, but in fact would be foolish not to acquire more land given the fact the US was actively trying to facilitate the Monroe Doctrine of removing the colonial powers from the Americas, and keeping the Europeans out. Compare the US and its brief imperialistic period where it mostly fought for control over islands in the pacific and the Caribbean such as the Philippines, Hawaii, Puerto Rico, etc. to the atrocities during the Opium Wars or the wars in Africa by the British, and you'll begin to realize that America is definitely more favorable than pretty much any other growing civilization of its power and resources of its day. If the Americas had all the beasts of burden, and the myriad of other advantages the old world had over the new, then it would have colonized and conquered. It is the luxury of modernity with nuclear weapons that we do not tend to see empires anymore, as any invasion or conquest would be met with global pushback and the means by which other nations and their allies can curb the power of growing institutions, or at least in theory, if China is anything to go by.
C) What happened to the Native Americans was not "cultural imperialism" any more than any other state would. It is innate to man that when he migrates, he spreads his culture with his and mixes his culture with the local elements. This has been true from Ancient China spreading its language to all of East Asia, Alexander spreading Greek culture from Sparta to India, Rome controlling all of Europe and the Mediterranean, the Omayyad and Abbasids turning all of the Middle East into a united Arabic-speaking, Islamic culture. If you unfairly malign the US for doing the same as every other successful civilization, it puts them to a moral standard that cannot be present in determining the innate nature in which people find themselves in due to things like inequality in resources, desire to expand, the cultural syncretism found in all peoples, etc.
As a final point, I find it hypocritical that you reject the American identity, yet vote in our elections and have the audacity to decide where we steer our country. If you hate America, wish to not be associated with it and reject any attempt to integrate with its cultural values, principals, and identity, why do you think you should have a say in what leaders we pick? If the tables were turned, where an American Indian tribe was having an election, such as is common with groups such as the Iroquois, and people who do not wish to be Iroquois, reject their cultural values, and do not care about the principals of their five nations, then it would be right for us to condemn that as unjust. What you have done is essentially, according to your own principals and values, interfered in another nation's elections.
You either can choose to have the American identity and be a citizen of the nation, with all the privileges and responsibilities that brings, or you don't have a right to determine the direction of our country or engage with the US government. If you really reject the American label, why not renounce your citizenship, as you have the right to do, instead of this two-faced charade in which you simultaneously decry America and yet participate in its institutions?