Does the Bible talk about collective salvation?

No it doesn’t. The Bible message is about individuals being responsible for their own choice and commitment to follow Christ (Luke 14:25-33; Galatians 2:19-20; Philippians 3:7-9). Even when in Acts large groups of people were saved at the same time, they were all individually baptised (Acts 2:41-42). Salvation is based on an individual’s response from their heart to recognising their need for it and God’s provision of it through His son (Romans 6:16-18)