Never much understood the whole US propaganda angle. Spartans as the US and Persians as Iranians/Iraqis breaks down quickly on inspection. Even the 'fight them at the Hot Gates instead of at home' doesn't mesh well with that nonsense 'fight the terrorists in Iraq instead of at home' spiel.
Which sort of brings me to my main complaint with the film - the politics. Now I like politics in my movies, but the genuine kind, not underdeveloped superficial politics (I'm looking at you Robin Hood).
Instead of the issue in Sparta being waiting until the Carnea is over and then sending the army - and thus have it be about timing (i.e., will the cavalry arrive in the nick of time?) - the movie changes the dynamic so that the Queen is trying to get the army sent period. But it does this without ever establishing how, when or why Sparta has changed it's stance from delayed march to non-intervention. The passivity of the Spartan council - having them be talked down to by the Queen - just makes them look stupid, and like the Jedi in the prequels, making supposedly wise folk look stupid for the purpose of plot is poor writing. One of their Kings has just thrown an envoy down a well - there is no going back, war is inevitable. But then there it is not and the story steps back from over that line and shows a debate. I find this sloppy and of course, it was an addition to the story. It's there to give the Queen something to do - but surely there could have been a better way to do this?
The concept of a politician playing the game to further delay the march to war is a good one, but this one plays politics to stop the march from happening at all. Two problems here. It's not clear what his motivation is (compare to Ephialtes for instance) and it's not clear why he has such pull amongst the Spartans (his oratory skills aren't demonstrated and his arguments aren't that good) or how his politics can affect Sparta's ability to go to war.
It also doesn't make sense that the council be on his side. They're Spartans. They love war. So why is a society based around war wanting peace? On the one hand the film shows a gung ho no retreat mentality for the Spartans, and then this willy nilly let's not hurt ourselves weak mindedness. The two are opposites.
This could have worked had they made the obstacle at home Sparta's other king (the city had two partner kings) who had a genuinely good reason for not wanting to march to the Hot Gates and Leonides (i.e., he wanted to attack one of the other cities, had another plan for where to go or hoped that Leonides would be killed).
Anyway, I'm rambling.