My personal conclusion is that the US is the least racist country in the world.
You just haven't had a broad enough experience of this country, where people are exceptionally friendly to strangers/visitors in general, and most of your time was spent in one state, to arrive at that conclusion.
Your statement is directly contradicted by the race-based politics and history of this country. That being said, I'll grant you there are many, many other countries where racism is currently worse than the US.
And even if your own experiences was enough evidence to draw such a conclusion, you haven't been to every other country, so you still couldn't say it's the least racist country in the world.