I don't think any nation is great; however I also thing you're vastly oversimplifying to the point of being wrong and unreasonable
No, the US wasn't formed by committing genocide, it developed with it as it gathered powers as many powers do. I could see the argument of Spain being largely violent to the point of genocidal from fairly early on in Central America, but that wasn't the case until later in US history. The early forming has conflict, but also cooperation, as American Indigenous nations had with each other. Treaties with American Indigenous nations were made by Britain and others in what is now the US, that's part of what led to conflict between the early colonists and the British government of the time. Some of the American Indigenous nations welcomed the Europeans, some leaders of those nations merrily trading their daughters as 'translators' for access to European weapons and other supplies to fight wars they were in with other nations - pretty standard for the time. Some other American Indigenous nations were defeated because they had been so brutal to their neighbours that those neighbours stepped aside and some helped the Europeans to defeat them. In the US War of Independence, some American Indigenous nations sided with the US, some with Britain, some tried to remain neutral, some fled - as did some who sided with Britain after the war. The genocide-manifest destiny comes later as the US government stabilizes power and wants to expand in the way of most powers have within its own borders and then beyond them - much as Britain's genocidal tendencies grew with power, remained largely within its own self-assumed growing borders until it gained enough stability with its neighbours to be violent elsewhere too.
A small percent of White Americans owned slaved, as did a smaller percentage of American Indigenous people and Black people. There was ongoing conflicts in the US about slavery from the start, and then there are things like the Barbary pirates situation where US ships alongside European towns being raided by Barbary pirates unless tributes were paid and those raids hat included taking people to Ottoman slave markets. The US's system was terrible. I think when Europeans point at it and act it was the pinnacle of evil, erasing both what Europeans did with slave trades and what was going on with the slave trades as a whole at the time, it hasn't done much good.
In the early days, many did not go willingly - it was used to dispose of prisoners, significantly more than were eventually sent to Australia, and then there is the whole indentured servitude system that one can never pay their way out of and at times could pass on to one's children. The idea that it great for all White men is a vast oversimplification.
I've lived in the US. I wouldn't go back, not because of its history, which I don't think is that unique, but because the current system and risks aren't ones I'm willing to face with my family.
Its like the UK...decendants of immigrants moaning about immigrants!
I hear this a lot. It is not the kindness to immigrants some seem to think is for a few reasons including that people who hate immigrants already call us invaders, an invading army, and so on, so equating modern immigrants with those repeated invasions of the UK is not helping. It also implies that immigrants and our children who speak negatively about other immigrants or the immigration system must be 'moaning' and in the wrong. I think we're quite well placed to discuss issues of immigration, the issues of and barriers to integration, the issues that the system is only working for those who are making money off of it with no concern for the wellbeing of either immigrants or British-born in our communities.