I am French and we end our phone conversations with the equivalent of a "bye".
I noticed however that in most of the US movies or TV series (especially the police/action ones), the callers just hang up after the last "meaningful" exchange.
A few examples here: https://www.youtube.com/watch?v=APUQeQalRsU
The movie conversations I have in mind are of the typical kind (not "help me!") - for instance the team is synching up on what to do next, or who does what. In such "work-oriented" situations, I would still end a call with a "bye", in normal life.
Is it really customary in the US to end phone calls without saying goodbye?
EDIT: Following some advice from @Tinkeringbell, I will repeat here my last comment about why my question deals with movies:
I live in France and despite having profusely travelled to the US (about 50 times, mostly Illinois, Arizona and California) I think I never saw anyone hang up a phone. So my gateway to such human interactions in the US mostly comes from movies (with the understanding that they are movies, of course). This is similar to someone in Japan who would see on TV French people continuously kissing to say hello and would wonder whether this is the norm (it is). There are not many real documentaries here about people using phones in the US :)