It always blows my mind to look at that graph. Almost even in 2017 and then it just plummets 30 points over the next 6 years. Nothing even changed, I don't see any discernable reason for it, it was just that the media decided to start shitting on China and making them public enemy #1 for a bit (sparking a massive "unexplained" rise in anti-Asian hate crimes). Obviously they got all the blame for COVID to distract from all the domestic policy failures, but the shift in public opinion started before that.
If you ask people why they suddenly had negative views of China, they'd just cite things like "China has billionaires," or "China saber-rattles over Taiwan," or other stuff that's been true for decades. Those things were just as true in 2017 when China had 43% favorability among Americans, or in 2011 when it was 52-37.
That's the power of propaganda.