Most of the 1600s and 1700s for New England. Quebec for longer, possibly the end of unit 1800s. That’s average number of children per woman, not an extended family. 1800s Ireland, which was probably poorer than the US has been since 1600 had similar fertility.

I still wouldn't say that is the norm, since the infant mortality rate was ~40%. And, if you're popping out a baby every 2 years, by the time you're on your 8th baby, your first-borns, should they have lived, would be nearly able-bodied adults with the ability to also work a bit to help support the household or going out and getting married.