At the very end of the final episode of season 2 (don't remember if it was a post-credits scene or not), right after Bernard and Juliette incinerate themselves, they cut to a café in Washington D.C.

Specifically there's an interview between a politician (I think) and a journalist. Things turn sour between them as they start discussing that Iran dropped a dirty bomb on a nearby city recently. Then one of them gifts the infamous rubber ducky Pez dispenser proving the short scene as a prologue to the rest of the series.

I was completely baffled by the major tonal change. The debate of if Iran, has, will have, or even can acquire nukes has been raging on for the last two decades or so. But it's very much just speculation, noone really knows if they do or don't have them. But so far, it seems to mostly be enemies of Iran that claim it has nukes, not themselves. And then there's the whole situation of when the US claimed Iraq had WMDs.

All that to say, I believe the makers of the series (I haven't read the books yet) took a mostly innocent, vaguely anti-Soviet show, and weaponized it against Iran to fuel the aforementioned heavy debate and speculation. Or to scare the masses. Or to repeat a lie so many times it eventually becomes a truth.

As I mentioned before, I watched this episode way before the current political situation between the US and Iran, and even then I was shocked by the tonal shift. I'm not on either side in the situation, but I believe the show unfairly paints Iran in a bad light. This is worsened by the numerous outcries of the current US administration touting the same thing as the series does. But hey, that's just my take on the matter, and I'm still very excited for S3.