Yes I know the EGR has been around for a long time, and I know that your Honda get's good gas mileage. I don't really care. You can look back at vehicles and the engines that went through the smog-revolution, and see clearly where power and fuel efficiency dropped as more emission control were added on. Case and point. Now auto manufactures have done an amazing job climbing out of that hole.
You are making broad assumptions that you know nothing about. Not everyone wants a cheap high gas mileage slug mobile. I don't, and many I know do not. Some do, that's your group.
Every car can not get 40 mpg. You are full of it. Go learn some physics. You need X amount of energy, to move Y amount of weight, Z distance. You can't just bend the laws of physics because you just know, because you know, that "all cars can get this.." no they can't.
People want a powerful engine. They don't like getting passed on the highway by school busses. They want to push the gas and feel the car launch. Yeah there's a few that would ride a lawn mower to work just to get 5 more miles per gallon, but you are the minority.
Not everyone cares soley about fuel stats. I don't care a wit about fuel stats. I love my luxobarge car. Yeah it get's 17 MPG and I enjoy every minute. I hate those tiny plastic 4 wheeled mopeds. I would take a 300M over almost anything Japan has ever offered. I would like an RX-8... likely not for the mileage.
So why do GM, Chrysler and Ford not make tiny plastic bannana eco-box 4 wheeled scooters? Because people like me, aka customer base, wouldn't buy one if it was the only thing they produced! But what about people like you? Why don't they build a few for your group?
Well opinions differ, but the answer isn't the crazy stuff you came up with. GM would sell a renamed Yugo if they could make money off it. GM doesn't care a wit as long as they can earn some money. The problem is, they can't make money. Why? This is where opinions differ. Some say Japanese autos are made with cheaper labor for their lowend cars. Some say the unions have raised the cost of labor so they can't make money on econo-cars. Some say regulations or taxes by our government make econo-cars unaffordable to make. Some even say that Japan's government helps subsidize domestic auto production.
No matter the case, you will never see our domestic companies making cheap econo-box plastic bannana 4 wheeled scooters, until they can make money doing so. As soon as it becomes profitable, you'll see them pour effort into them. Until then they will only build what they can make money on and sell. If people are not willing to buy, or if they can sell them but only at a loss, then they will not make them.