This was the whole premise of this discussion, which you linked to previously… Touch move by player who is not on move
However, since you specifically mentioned “Blitz” in the title of your post, the USCF Blitz rules does have Rule 15, “A legal move is completed when the hand leaves the piece.” So for blitz games the answer is actually the same as the FIDE Laws, the next player is “on the move” when the player’s hand has left the piece, assuming the move was legal.
In my humble opinion, USCF needs to change their regular rules on when a player is “on the move” to the same as FIDE’s, e.g. after the opponent had ‘made their move’. FIDE deliberately puts this in Article 1 because a clock only comes into the equation via the “Competitive Rules of Play” from Article 6 and beyond. The USCF definition of a player being on the move after it is completed by pressing their clock is irrelevant and very confusing if a clock is not in use. And yes, I’ve overseen USCF rated games without a clock being used.