Based on the provided statements, Species C would most likely be classified as an invasive species in the United States.
Species C is a plant from Japan that was introduced for beneficial purposes, such as reducing soil erosion, but it exhibits invasive behavior by growing up to a foot per day, smothering low-growing plants, killing trees, and lacking natural predators. These characteristics make it capable of causing significant ecological disruption, which is a defining trait of invasive species.
The other species either do not exhibit harmful invasive characteristics, or they are beneficial in their new environment, which makes them less likely to be classified as invasive.