Complex sentence: U.S. automakers had first countered imports such as the Volkswagen Beetle with compact cars including the Ford Falcon, Chevrolet Corvair and Plymouth Valiant, although these cars had six-cylinder engines and actually comprised a larger class of vehicles.
Split into simpler sentences: U.S. automakers had first countered imports such as the Volkswagen Beetle with compact cars including the Ford Falcon, Chevrolet Corvair and Plymouth Valiant. These cars had six-cylinder engines, but actually comprised a larger class of vehicles.