I will be arriving at Narita on American Airlines at 3:05.
I need to catch a Delta flight at 5:25.
Is this enough time?
American airlines almost always operates out of terminal 2 (not certain code share flights). Delta almost always operates out of terminal 1 (not certain code share flights). So you will arrive in terminal 2 at 3:05 and have a little more than 2 hours before your flight leaves from terminal 1.
Here is a very handy guide for procedures when arriving at terminal 2. After getting of the plane you just follow signs for International transfers. (I am assuming given your choice of airlines). There you will have to go through a security check and an x-ray of your carry one baggage.
From there it is easy to use the Terminal shuttle bus to get to terminal 1. The buss takes about 15 minutes to get to the terminal. When you get to your new terminal just check for the gate and proceed to it.
So yes. Unless something spectacular happens, it does not take even close to 2 hours to go through security and take a 15 minute bus ride. But as one should always do in case of transfers walk straight to the security line then take the bus as fast as you can.
Normally this will leave you plenty of time in your new terminal to browse or get some rest. But in case of lines you will be as fast as you can.
IF, by any chance you inbound flight is running late it is quite common that someone would be standing at your path to security or at security and check for people with short connections and help them as much as they can.