If you choose to ignore numerous human rights abuses that started before independence and lasted until about 1965 then you probably do have model for a really great country, but you can't rewrite history and reality has to be accepted.
Slavery 1619-1865
Displacement of Native Americans 1600s-1800s
Jim Crow 1870s-1965
Asian immigrants expelled from California towns (1880s)
Lynching 1882-1964 (up until 1935 there were lynchings in the double digits)
Japanese Internment (1940s)
Legal citizens deported in Operation Wetback (1950s)
That is a terrible human rights record for a first world nation even if it is in the past. There is nothing wrong with acknowledging that the country is not perfect and has become better over the past few decades. Cuomo is not even going to come remotely close to losing over this and his presidential campaign probably won't go anywhere but that is because he hasn't been as liberal as some Democrats would like.