The US is able to mention its past mistakes.
China still can't talk about students it murdered over 30 years ago.
Yet, recent American presidents have no problem admitting that Afghanistan and Iraq wars weren't the best of ideas.
The entire point of being able to mention past mistakes is for future generations to be able to learn from them and avoid making the same mistakes. It seems, in recent times, that while this liberty is "afforded" to US/Europe, they're not able to use it effectively, if at all. Meanwhile, even though the Chinese might not be able to talk about their mistakes publicly, it seems evident from their progress and events that they have not forgotten them, and that it is in their minds, at the very least.
Edit: Not to mention, looking at how your current president is going after Canada just because of an ad, don't keep your hopes up on US citizens being able to "mention" things either.
It's really quite interesting to see China being labelled as imperialist mean while the western powers have been colonizing and meddling in all kinds of affairs for generations... (see Operation Northwoods as one example)