China and India's commitment is tied to GDP. As the Wall Street Journal noted, "China won’t even begin reducing emissions until 2030 and in the next five years it will use more coal."

Not only that, but the article goes on to note that some countries simply sidestep their obligations, but we can't due to our legal culture:

President Obama, meanwhile, committed the U.S. to reducing emissions by between 26% and 28% below 2005 levels by 2025. This would require extreme changes in energy use. Even Mr. Obama’s bevy of anti-carbon regulations would get the U.S. to a mere 45% of its target.

Meeting the goals would require the Environmental Protection Agency to impose stringent emissions controls on vast stretches of the economy including steel production, farm soil management and enteric fermentation (i.e., cow flatulence). Don’t laugh—California’s Air Resources Board is issuing regulations to curb bovine burping to meet its climate goals.

Advocates in the White House for remaining in Paris claim the U.S. has the right to unilaterally reduce Mr. Obama’s emissions commitments. They say stay in and avoid the political meltdown while rewriting the U.S. targets.

But Article 4, paragraph 11 of the accord says “a party may at any time adjust its existing nationally determined contribution with a view to enhancing its level of ambition.” There is no comparable language permitting a reduction in national targets.

Rest assured that the Sierra Club and other greens will sue under the Section 115 “international air pollution” provision of the Clean Air Act to force the Trump Administration to enforce the Paris standards. The “voluntary” talk will vanish amid the hunt for judges to rule that Section 115 commands the U.S. to reduce emissions that “endanger” foreign countries if those countries reciprocate under Paris. After his experience with the travel ban, Mr. Trump should understand that legal danger.

Not only that, but many countries in the "developing world" receive subsidies and credits under the Paris Treaty. So no, it doesn't hurt everyone's economy. A combination of the way the treaty is written and the way our country works ensures that signing it would hurt us, and disproportionately so.