4...Nf6 allows the knight attack, which threatens what happened in the game. In order to prevent that, the line goes something like 4...d5 5.exd5 5. Na5 Bb5+ 6.c6 etc....which idk, it's fine for black, but maybe a bit annoying, and maybe simpler to just avoid it by playing the bishop out instead of the knight.
Unsure where I blundered

Piedraven: when white played 4. Ng5, you apparently thought for 17 seconds, and then you played Be7. What were you thinking about? What was your plan after Nxf7 of Bxf7+? Just to resign? Or did you not notice those moves at all?

try Bc5 instead of Nf6
...Nf6 is a fine move. The alternative ...Bc5 is also fine, but just different. I have played both by repertoire in the past (started with ...Bc5 and switched to ...Nf6 and now I don't even play 1. e4 e5 with the black pieces too often, so I hardly get this position at all).
Personally, I like ...Nf6 of those two options though. @ice_cream_cake nailed it with the importance of the ...d5 move (the variation they named is the Polerio Defense which is what I used to play back when I used ...Nf6).

Piedraven: when white played 4. Ng5, you apparently thought for 17 seconds, and then you played Be7. What were you thinking about? What was your plan after Nxf7 of Bxf7+? Just to resign? Or did you not notice those moves at all?
I can't remember. I think my mind just went a bit blank and I tried salvaging things and then went on autopilot.

I've run out of available game analyses for the day, but I'm reasonably sure I made a gigantic blunder somewhere here. I can't analyze which exact move was the blunder until tomorrow. Any thoughts?
Be7 allows a knight fork, I would say that is where the blunder is.
Another line of the italian is this (traxler)
After which, the game is drawn at best for white, if he finds the best move every single time, which is v.hard.
no,
at least +1 for white either way

4...Nf6 allows the knight attack, which threatens what happened in the game. In order to prevent that, the line goes something like 4...d5 5.exd5 5. Na5 Bb5+ 6.c6 etc....which idk, it's fine for black, but maybe a bit annoying, and maybe simpler to just avoid it by playing the bishop out instead of the knight.
its right! but tbh, d5 xed5 na5 etc, is pretty good for black as white loses almost all development for a pawn
I've run out of available game analyses for the day, but I'm reasonably sure I made a gigantic blunder somewhere here. I can't analyze which exact move was the blunder until tomorrow. Any thoughts?