You make a lot of great points, but I think framing the discussion around the meaning of the word "is" isn't a great idea.

Is the United States a racist country? Well, is racism something that is either "yes" or "no", with no other meaningful distinctions?

I'm quite sympathetic to your argument--the racist events, policies, actions, etc. that you mention are real and should stop.

But I'm not sure the argument isn't even stronger the other way. What about this one:

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America is not a racist country. We believe that all people are created equal. Every time prejudices have compromised this critical principle, people of strong moral character have, often at great cost, forced us to confront the ugly reality, to make meaningful changes, and to ever more strongly reaffirm this principle: people are created equal. This is the legacy of the country: throwing off the horrors of slavery and tackling racist thought and institutions.

America is not a racist country. We were founded with glorious principles and grotesque "compromises", and the principles won. But there is still racism. That is why we will, why we must take up the cause again--there are still too many ways in which we fall cruelly short of our ideal, of who we are.

America is not a racist coutry. We will take up the cause again and again; we will fight the lingering stains of racism until it is exiled to the pages of our history books. Because we must be true to our ideals, and we are not a racist country.

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Makes a pretty strong argument, doesn't it? It dovetails nicely into specific policy objectives that reduce current problems like racial profiling in policing, lending, and so on.

So, really, it depends on what you mean by "is". There's certainly some significant racism left. By deciding it doesn't meet the threshold of "is", you get to argue that opposing racial injustice is core to what it means to be on the right side of American history. It obliterates the superficial arguments by white supremacists or vested interests that it's all just driven by people who hate freedom and hate America. I think it's a much better way to effect change, and a more accurate (though not so clear as to be unarguable) historical perspective.