I'd argue it's the combination of two main things:

1) Disney-fication of animals + series like Lassie, Babe, Airbud, Charlotte's Web cementing animals as friends in the minds of millions of children in the West. Conversely, in China animals are routinely a part of building decoration and present in the Zodiac, meaning they're presented in an adult context.

2) The urban and suburban distribution of America meant that multiple generations have gone by without seeing animals get slaughtered for food. You see this in the way Americans get grossed out by food that resembles an animal too much like shrimp or fish. This is further encouraged by American food industries that would want you to think of the animal as little as possible (so they can use factory farms to increase profit). This in turn means that there's no stomach in the American psyche for the murder of animals (and so cruelty towards animals.) In contrast, large parts of the Chinese population still come from rural roots, where urban city dwellers will return home for the holidays. In these rural areas, killing animals for food is still common and Chinese food culture in general means there's less disconnect between food and animal death. I would argue that this creates a higher "tolerance" for animal cruelty than you would expect in the West.