I have booked a trip from Stockholm to Newark airport. I have bought separate tickets for my domestic flight to Alabama. I will arrive in Newark 1 pm and my domestic flight is at 7 pm. That gives me about 6 hours to pick up my luggage, change terminal, check in and board again. Will I make it? What terminal would I arrive in (international) and what terminal would I fly from (domestic)
Two hours is typically plenty.
But if your flight is significantly delayed, like for 8 hours, nothing helps. This is a small chance, but not predicable.
Personally, I have often done such combinations, and I feel comfortable with a 4 hours; never failed yet.