Iran’s supreme leader on Saturday threatened Israel and the U.S. with “a crushing response” over attacks on Iran and its allies.
“The enemies, whether the Zionist regime or the United States of America, will definitely receive a crushing response to what they are doing to Iran and the Iranian nation and to the resistance front,” Khamenei said in video released by Iranian state media.
Outside of the Revolutionary War and the War of 1812, no adversary in war has ever had the military ability to significantly impact the contiguous US, and while that may well happen one day, it isn’t gonna be Iran of 2024 who changes that run.
It’s also not likely that any country will have that ability near term outside of a preemptive nuclear strike, and a country set on doing that has to be able to counter or accept the US response, which I don’t anticipate any country doing in the near future.
https://www.vice.com/en/article/we-asked-a-military-expert-if-the-whole-world-could-conquer-the-united-states/
More-realistic concerns might be terrorism or economic pressure.