Yes, there is a new contract created every month. Feel free to quote Italian conditions, but in the US a contract requires consideration, which occurs on a monthly basis.
In any case, it doesn't affect the ethics, and Netflix gives ample time for a customer to cancel renewals.
Forget about the law. Ethically, Netflix is in the right. Someone signs up and pays for a month. They get a month of service. That continues month to month. At some point, Netflix tells them "it will cost more next month, if you don't want to pay more, you can simply cancel and not pay." There's no force or deceit. Continuing to pay and then coming back later and suing Netflix is an attempt at theft, plain and simple. The law is unethical.