Of course, what submarine based Trident gives you is the time to take stock. A leader (if there is one left) doesn't have to make an immediate decision. He/she can look at the options. He/she can say to Iran. Hand over all those responsible or we will blame you all. Give them 24 hours.
With Trident he/she can also choose to pick the target and the yield. Maybe a single low yield warhead on a key military installation?
Back this up with none nuclear strikes from your CVF rushing to the area.