It was my understanding the US bombs production and management facilities ran tests until simulations were good analogues of what they saw in the real test, at which point it's both cheaper and faster to run simulations.
The only possible reason to run real tests, is for a political communication, although who is receiving it and what it says to them, isn't clear.
if a nuclear submarine launches a tomahawk with a non-nuclear warhead is the entire weapons system "a nuclear weapon" in your eyes? Is that a breach of the arms treaties, and breaches "no first strike" posture and invites second strike response with nuclear warheads?
Apparently you haven't noticed that Tramp has been purging anyone loyal to the United States as a country and installing subservient apparatchiks in their place. This is not a dynamic which selects for intelligence, competence, or subject matter focus.
Unless there are some shot holes prepped, there is a bit of engineering to get there first. "As quickly as possible" is slow, unless you repudiate the other treaty and do an above ground or underwater shot which the US hasn't done since 1992 and even then it was basically a buried one. It hasn't done an underwater test for far longer.
Real life isnt a Tom Clancy novel. Jack Ryan wont save the day.
What made this movie suspenseful* for me was not how realistic it was, but how only half of it was realistic and the other half was completely disconnected from reality. A random incoming nuke of unknown origin, I can easily buy that happening. A deliberative process among highly competent officials deciding on a response, sorry but that is just not real life. Maybe it was at some point in our past, but certainly not in 2025.
As for the ending, it felt like a cop-out to me, but it didn't really matter to me.
*suspenseful, but not good.
How were you talking about anyone but policymakers?