Amazon.com Inc., the world’s largest Internet retailer, said it will sever ties with its affiliates in California if the state enacts a new law that requires the company to collect taxes on online purchases. California Governor Jerry Brown signed legislation yesterday mandating sales-tax collections by Web retailers, including Amazon, on purchases by state residents. The state’s pending budget plan counts on $200 million from the law. In an e-mail before the bill was signed, Amazon said the legislation was “unconstitutional and counterproductive.”