Thanks for the suggestion, but unfortunately, just having his birth certificate isn’t enough in my case. The issue is that he didn’t meet the requirement of living in the US for at least 10 years, with 5 of those years after his 14th birthday. That’s where I’m getting stuck, and it’s why proving his citizenship through other means is so challenging for me.
I think you have misunderstood the statute. There's no timetable for his US citizenship to kick in. If he was born in the US he is a US citizen from birth. I wish I could explain it to you better.