The big three meet the same emission and fuel standards as everyone else. Their two main problems are: 1. they negotiated with the slacker unions, letting them get out of hand. 2. the feds get in their way.
I will continue to state...the most powerful agent for change isn't the feds, it's peer pressure. When, or more accurately if we want teeny weeny cars...we will get them and because the market place (us) is demanding it...the cast per unit will be next to nothing. The cost of compliance to a law or regulation is much higher than the cost of providing the market it's choice.