How did America go from a nation that joined WW2 to a nation where a lot of people want to be neutral in a war between America and China?

It seems like a lot of Americans do not want to go to war with China ever even if it would benefit America, why is that? Most Americans in the 1930s and 40s did not want to fight Nazi Germany but once Pearl Harbor happened they joined the war effort because they knew it was the right thing to do. But the war with China would be much worse, it would be a war between two nuclear superpowers that could turn into a world war. Many Americans would rather stay neutral and let China take Taiwan and Southeast Asia without much opposition.