If fully implemented, the rules would have cut oil consumption by about 12 billion barrels and reduced carbon dioxide pollution by about six billion tons over the lifetime of all the cars affected by the regulations, according to E.P.A. projections.

The rules also would have put the United States, historically a laggard in fuel economy regulations, at the forefront worldwide in the manufacture of electric and highly fuel efficient vehicles. The United States and Canada are the only major nations that have adopted mandatory emissions standards through 2025. The European Union has only recently proposed standards for 2025 and 2030, while China has only started to work on standards for those years.

Source: E.P.A. Prepares to Roll Back Rules Requiring Cars to Be Cleaner and More Efficient - The New York Times

Simple: don’t buy another vehicle that doesn’t get at least 40 MPG and the regulation doesn’t matter.

I still don’t understand all the people who tell me that electric cars or plug-in hybrids are too expensive and then I find out they drive a $40,000 SUV or truck that gets 15-20 MPG. That’s way more than a reasonable plug-in.