(But I disagree with the meme. Saying you are not allowed to satirically compare asians with characters that happen to be yellow is a problematic statement in itself.)
Except that centuries ago the Europeans decided to start the Yellow Peril campaign to strip Asians of their humanity by calling them the 'yellow danger', which still has its effects today. Other than being a yellow bear there is nothing noteworthy comparing Xi to Winnie. Do better. Would it be okay for you to satirically compare black people with characters that 'happen to be black'?
The comparison stems from the general physique and perceived mannerisms that supposedly match between the two. I'm not sure the colour was an original part of the meme anyway. The origin was that image of Xi and Obama walking alongside each other, with the drawing of Pooh and Tigger to show how similar of an image it was. Xi was not coloured yellow in those earlier images, that started after the CCP cracked down on those memes.
The origins of the meme may very well be harmless. It started on Chinese social media AFAIK. Westerners going on a run with the meme is what made it problematic.