The search-engine firm announced earlier this week that it will be ending the consumer version of Google+, while the company also pledged to improve its data-sharing policies after a leak of private data.
Google may not have been legally required to acknowledge the incident, but senators have expressed their concern.
A letter from the senators reads: "As the Senate Commerce Committee works toward legislation that establishes a nationwide privacy framework to protect consumer data, improving transparency will be an essential pillar of the effort to restore Americans' faith in the services they use.
"It is for this reason that the reported contents of Google's internal memo are so troubling."
Despite announcing its plan to shut the consumer version of Google+, the world-famous tech firm said the "enterprise" version of the social network would remain open for businesses to allow colleagues to communicate.
Google said: "Our review showed that Google+ is better suited as an enterprise product where co-workers can engage in internal discussions on a secure corporate social network.
"Enterprise customers can set common access rules, and use central controls, for their entire organisation. We've decided to focus on our enterprise efforts and will be launching new features purpose-built for businesses."