From what I can tell (outsider perspective, I know) - Barack Obama did nothing particularly wrong; he just couldn't get anything done in the country because Republicans in Congress always completely refused to agree to anything he suggested, and refused to compromise.

The title is racist and the contents of the OP are ignorant. Are you trolling?

He's set America back 20-50 years

Most of the world does not think he did a horrible job. He also still has three years left, so we shouldn't exactly be using the past tense.

People who are racists are usually idiots, so i suspect that it could possibly as said idiots will just think "well all black people are the same, and obama did nothing right so none of them can".

Disclaimer, I am going on the assumption that he did nothing right from what you said because I don't actually know, as I live in Australia and don't take much notice of America

No, I think his election just cemented further ignorance among Americans. He was mainly elected because he was black, not for his policies or anything, but vague promises of change.

If anything it just portrays Americans as even dumber than before.

But there is no way he set blacks back, definitely improved race relations. He's just a shit president in general.

What the president does right or wrong is largely subjective.  Let's say that.  It depends on how you feel his actions were the time he made them.  Also, "right" decisions don't always have to yield positive results.  A "right" decision can simply be a decision that best fit a scenario where only bad things can happen.

Lol no. Republicans in Congress has kept us int he Bush era.

The alternative was Mitt Romney and Paul Ryan: I'll take Obama any day.

In thefirst election, our vice preisdent would've been Sarah Palin: again knowing the situation we're in now  - I'd still Choose Obama Biden.

Never said that "African American" was the racist part.  I think it's racist to assume that "African Americans" can be set back, and that how Obama seems to be portrayed will be a reflection of African Americans "progress" in society.