The Ford Focus is still a 3000-pound car these days. Even "economy" cars these days are rather heavy, and you'd be surprised how little those 70s cars weighed. Old Mustangs are positively lightweight. While the land boats are mostly gone, cars in general have gotten larger and especially heavier, even with lightweight technologies and materials used to offset the increase.
The way I read it, the OP was talking about people needing to drive micro-cars (e.g., ones that can only hold 2 people, like the micro-cars that are only sold in Japan). Those cars would fare very poorly in a crash against just about any typical car (let alone SUV) on an American road.
