The earliest Limo Bus for NRT departs HND T3 at 6:40 AM, getting you to NRT T2 at 8:00 AM.
If you can make it onto the 5:51 AM Keikyu Express train, you could get to NRT at 7:36 AM.

There are other flights arriving around that time. You probably won't be the first, so you should expect to join a queue at immigration. I think you're likely to make the 6:38 bus but the 5:51 AM train is less certain.​​​​​​
I would expect the bus to run on time unless there's bad weather. The roads get a little busier in the last couple of weeks of December as businesses wrap up the year, but you're not going to encounter traffic at that time on a Sunday morning.
The major holiday in Japan is New Years. Christmas is a regular business day.

EDIT: I would only do this if both flights are on the same ticket.
If your flight from NY is delayed, or it takes forever to get through immigration, you could ask JAL to put you on a flight from HND to TSA, which (I imagine) would be just fine.