Good point! Indeed, if the original poster is on Aeroflot metal (DL Codeshare) the arrival will be at Terminal 1. If that is the case the poster will need to exit Terminal 1 and take the AirTrain one or two stops to Terminal 2 or Terminal 4, where one can go thru security for Delta flights. This should still be pretty quick.

Alternatively it is possible to walk (probably preferable as well) from Terminal 1 to Terminal 2 as they are right next to each other. Just turn right outside the arrivals level and keep walking - you'll hit Terminal 2 in 2-3 minutes. This is likely what I'd do.

In closing, I wouldn't worry too much about the terminal changes as the AirtTrain stops at all terminals landside (pre-security), T4 & T2 are connected by bus airside (post security), and lastly T1 is literally right next to T2. The main time-sucks tend to be customs and security. 4 hours, of course, is much more than enough!!

Anecdotally I got thru JFK customs in 15 minutes last month - the passport scanning machines are a huge improvement!