The internet search leader had already faced tensions with lawmakers after it decided against sending its top executive to testify at a hearing on privacy and data protection, prompting the committee to leave an empty seat for the company.
Google has also been in the crosshairs of US president Donald Trump, who alleged that its search results were biased against conservatives, although there was little evidence to support the claim.
The rising tensions come with Google holding an event in New York widely expected to release its Pixel 3, the upgraded premium smartphone that aims to compete with high-end devices from Apple and Samsung.
The Pixel phone is part of a suite of hardware products Google is releasing as part of an effort to keep consumers in its mobile ecosystem and challenge rivals like Apple and Amazon.
On Monday, Google said it was unable to confirm which accounts were affected by the bug, but an analysis indicated it could have been as many as 500,000 Google+ accounts.