No-one ever said that it's all Trump's fault, but the US is one of the top CO2 emitters and Trump is a climate change denier, so he is a deserving target as well as China. Saying one is bad doesn't excuse the other.

While China produces the highest amount of net* co2. Per capita they are much lower, ranking around #13. Germany, Japan and Poland, all have higher co2 emissions per capita. The US produces about 1/2 the amount of co2 as China with only 1/4 of the population. Meaning that the average American has about twice the carbon foot print the average person in China has. Nuance matters.

America also produces Carbon emissons and what not. It would be like saying their is no need for a border wall cause half of all ilegal immigrants come in legally and over stay their visa.