Spoilers will dwell beneath the break along.
Before I get to the IR of it, I should say that I am a bit biased as I couldn't really enjoy Letitia Wright's performance given her anti-vax politics stuff. That and the movie was super-long. The movie was about grief, which is, um, not fun. So, it was a good memorial for Chadwick Boseman, but it was not that enjoyable of a movie. They did a good job with Namor being an asshole--keeping to his comic book roots.
So, onto the IR of it:
I get that France is one of the bad guys, looking to plunder Africa. Absolutely. The US seemed just a wee bit trigger happy about going to war over vibranium. That was never really well-explained--none of the US side of things made much sense.
But the big IR thing here is Namor's view of alliances: he wanted Wakanda to join him in his war on the surface world. Or he would make Wakanda his first target. To be fair, the idea that you can threaten countries into submission is an old one, but it runs against the fundamental dynamics of international relations--that countries will balance against threats, not join them. One could cite Waltz or Walt for this. Who adopted this idea of threatening folks into submission? Kaiser Wilhelm thought that he could threaten the British into submission before WWII, and that did not work so well for him. More recently, Putin had hoped (and hope is not a plan) that he would keep NATO from supporting Ukraine via some nuclear sabre rattling. That hasn't worked out well for Vlad. As Waltz argued long ago, if you ally with the stronger (in Walt's theory--more threatening) side, you have to depend on the good will of the stronger side, and, in international relations, you should never be in a position to depend on the good will of anyone.
In the movie, Wakanda resists. Namor tells Namora (really?) that it will work out in the end--that when countries attack Wakanda, Shurri will reach out to Namor and his people. Maybe. I guess BP3 would be the movie where the US attacks Wakanda? For Vibranium?
One last thing: Namor is not the only bad planner. Shuri proposes to set a trap for Namor ... at sea. Not great when that is the other side's home
turf surf. Her people were doomed except for the last minute peace deal.
I won't even get into the UN stuff, which was just silly.
So, not great IR. Nor any principal-agent stuff to make fun of. See the movie for the moving tribute to Chadwick. Don't think too hard about the bad international relations and alliance politics.