Deterrence is not totally lost but damaged after Gazans, Hezbollah, and Syria greatly damaged or lost. Israelis finally launched a front attack after decades of very hostile posturing between the two countries. That is not a coincidence!
As for the America factor: No country without potent payback is willing to have a frontal war with America. Only countries like Russia and China dare confront America directly. Iranian leadership knows that.
Anyway, Iran needs to massively rebuild its missiles, flush out the spies/saboteurs, build its air defense system and maybe stay out of the Palestinian Cause going forward. Look eastward.