The United States is a melting pot of all the world's races and ethnicities. I believe that race relations within the United States are much more complex than race relations within Europe. There is just a lot of diversity when it comes to race in the United States, more than in Europe, which makes race relations more complex.
Race relations in the United States of America are less complex than those in Europe. This is only because of one simple reason, the United States of America is a single county, while Europe consists of many countries. This makes it more complicated in Europe then in the Unites States.
There are a lot of race relation issues in America, but we also have a very ethnically diverse group of individuals in a huge population. I think Europe has more complex problems because they are multiple racial groups as well as historically cultural groups, roma, that can be difficult to meld together.
I do not believe there is a difference in race relations between the United States and Europe. Americans and Europeans face similar situations regarding race relations and the influx of different migrations. There is no reason to believe that one group faces more complex situations. There's no measurable difference between them.
Race relations in the United States are far less complex than in Europe. France has banned or limited certain groups. The United Kingdom has considered limits on wearing hijabs in public. The Roma people are discriminated against all the time. One just has to look towards the ethnic cleansing in the Balkans in the mid-1990s to see that Europe's race relations are marked by traditional fears among regional groups. Contrarily, the United States isn't perfect but at least we don't have a "black" state and an "Irish" state in America.