I'd argue that the woke left is doing it in comparison to utopia. The more moderate left does it in comparison to Europe.
Although, to your point, the woke left never holds countries other than the United States to the standards that they hold the United States to.
Listening to them talk, you'd think that the United States is the only place on Earth where slavery or racism has ever existed, or the only country that has ever taken land that belonged to someone else. They know that human civilizations generally throughout history, not just the United States, has done those things. However, it doesn't advance their political narrative to mention that, so they just don't mention it. It's in their interest to paint the United States as this one-off, uniquely evil place.