I stole this from Reddit
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The estimate for the post-Gold Cup rankings is:
Team Points
Mexico1 607
USA 1546
Costa Rica 1440
Jamaica 1423
Honduras 1348
El Salvador 1343
Panama 1332
Canada 1311
Curacao 1309
Haiti 1291
T&T 1260
As you might be able to tell from the current rankings, not much changed due to the Gold Cup. Only difference really is that Haiti moved up over T&T (understandable given their performances). Keep in mind how little things changed, then take into account the following: it's going to be a lot harder to move up in the Nations League as the point multiplier is less than half that (15) of the Gold Cup (35). That means that at best teams can expect maybe a 7 point boost per match... likely to be a lot less if it's against weak opposition.
What does this mean?
Mexico, USA, Costa Rica, and Jamaica are effectively locks to get into the Hex. Nobody below them is going to get close to 1423.
Honduras has a decent cushion and has little to lose and much to gain from NL play. They have a non-FIFA member (Martinique) in their group and a team on a downward spiral (T&T). They are favorites to top their group, which means they could make the NL knockouts (at that point, you can't lose points, you can only win points). So Honduras aren't locks, but they're 80% the way there.
El Salvador are in League B so they get 6 competitive fixtures compared to 4 for all the other contenders. They're also facing teams they should be beating. That could translate into a 6-match winning streak (though against weak opposition) that should bump them 12 points or so.
Panama has the best shot at breaking into the Hex as they are only 11 or so points shy of El Salvador. However they will be contending with the fact that (a) El Salvador is likely to cruise to at least a 10 point bump from playing in League B, and (b) they have to face Mexico in the NL so are unlikely to make it to the NL knockouts. Panama will probably come away from the NL with even points and not catch up to El Salvador.
Canada and Curacao could theoretically break in, but it's just too unlikely. They're looking at probably a 40 point gap with sixth, but only really have ~45 points they could realistically make. Their path to the Hex would absolutely involve more than one win against USA/Mexico/Costa Rica.
Haiti can't make it in. Too large a deficit at 50+ points.
I am ignoring potential friendlies because they have an even lower multiplier than the Nations League matches and thus are unlikely to move the needle much unless Panama/Canada/Curacao schedule friendlies against top 20 teams AND beat them.
TL;DR USA, Mexico, Costa Rica and Jamaica are locks. Honduras and El Salvador will almost certainly make it in, barring a Panama resurgence. Canada and Curacao just have too large a points deficit to overcome.