In America despite the country going full force into the diversity experiment its seeing its own issues, its jury system is strained, take the recent example the Karmelo Anthony trial where multiple potential African American jurors were disqualified because they openly said they would not convict a fellow African American no matter what, the trial of OJ Simpson, where the African American jury openly said he was acquitted as revenge for Rodney King. In the west and south West the mass influx of migrants from central and south America has led to many of the people there never having to learn English which means they aren't assimilating, when they protest they wave foreign flags, they speak of reconquest by immigration of lost lands during the Mexican American war.
American can for now hold it together because its the world hegemon and richest nation on earth, a status it gained only because the entire industrialized world destroyed itself in ww2 and the rest of the world was functionally Agrarian farmers, America did not earn its position through the power of diversity, it earned it through luck, god tier geography, and early access to the industrial revolution, if America begins to suffer a soviet style collapse you will see the country break along racial, ethnic and cultural lines.