It looks like Delta is in Terminal 1 at Barajas and Ryanair is also, so that is of some help.
With that, it starts to come down to things like:
- is your inbound flight on time
- where are you sitting in the plane
- will you be able to use the e-passport gates (it's not clear it works for US citizens yet)
- Ryanair check-in lines (probably not short)
If you can manage with carry-on bags, that will also help. Barring that, it could work at
2:45, but since the variables cannot really be quantified until the day of the flight, I don't
think a definitive answer is possible. But you're definitely not in the clear.