The US lawmakers supposed to know what can be called securities easily. But it is true that, that is the work of the SEC. I think if ethereum is not a security, it will be a commodity. From the differences between securities and commodities, you can easily know that ethereum is a security. It is centralized and highly influenced by its founder. Second is that some ethereum was sold as an ICO. Ethereum blockchain as of today is proof of service. Some people may want to deny that ethereum is not a security but it is.