The current tiebreaker of using PD is flawed for many reasons, but I want to address it for NT specifically in this thread. I think it should be changed for club as well, but that conversation would be very different.
The current NT tiebreakers flaws were on full display in the Americas championships for NT this season. In Pool D, Mexico, Argentina and the United States all were set to only have one loss (each to each other) and thus be in a three way tie. So it was going to come down to PD for which 2 would advance to the semifinals.
This is where things got messy. Uruguay forgot to set a lineup against Mexico and thus Mexico was able to win that game by a much higher PD than they otherwise would have. Finally, in the final games of the season Mexico faced a TIE from Peru (who had no reason not to CT at this moment) which lead to them then winning another blowout game by more than they otherwise would have. Additionally, Argentina faced lower effort from Uruguay while the USA faced a CT from Costa Rica (managed by an Argentina manager).
Throughout this time all managers of the teams have been contacting each other and in many cases asking the team that is already out of contention to throw the game. This is further complicated by the fact that managers of smaller nations often come from the bigger nations and would be more receptive to playing in a way that benefits their home nation (see Argentina and Costa Rica). The PD against the entire group matters which means the teams that are already out, with nothing to lose have the ability to dictate who moves on.
My proposal, change the tiebreaker so that we first consider only the games between the teams tied. Here is what it should be:
1. H2H record among teams tied
2. H2H PD among teams tied
3. Total PD in the group
4. Most points scored in the group
This would make it so the games that matter are the games among the teams that can possibly advance. This prevents other nations from throwing games in order to help someone move on.
If the current rules stand, then there is an incentive for managers in the larger countries to seek to win smaller nations elections in order to be able to help their home country with PD. Additionally, we will have many situations like this season where teams try to get their opponent to throw the game for them or seek to make deals (I know that the USA, Argentina, and Mexico managers all were in contact with their opponents). The current system is flawed and leads to uncompetitive actions choosing who moves on in the group.