"traditional" US cars - so massive SUVs and trucks with 7.0L V8 engines are not popular because of their sheer size(a car which is "normal" by US standards, like Dodge Ram, can barely fit on an average UK street), fuel economy and insurance - people buy cars with tiny engines like 1.2/1.6L partially because they are more efficient,but also because owning a car with a >2.0L engine would make your insurance and road tax huge(and I am saying that as a person who used to own a 4.4L V8 car in the UK).