No, they won’t have to “custom build cars for each state,” any more than they do now. Ever notice how many foods have a label reading “eg. Penna. Dept. Agr.”? Pennsylvania passed a law ages ago with high standards, and pretty much everyone goes along (they don’t do all the inspection themselves). All it means is that the standards will go up everywhere, because most automakers will want to make their manufacturing and selling as efficient as possible. Window tinting is relatively minor. Raising the fuel-efficiency standards, however, is a big deal.
No, they won’t have to “custom build cars for each state,” any more than they do now. Ever notice how many foods have a label reading “eg. Penna. Dept. Agr.”? Pennsylvania passed a law ages ago with high standards, and pretty much everyone goes along (they don’t do all the inspection themselves). All it means is that the standards will go up everywhere, because most automakers will want to make their manufacturing and selling as efficient as possible. Window tinting is relatively minor. Raising the fuel-efficiency standards, however, is a big deal.