I am keenly interested in this issue. So, I will address a few branches of comments based on the original question.
1. Is Iran the king of the north, south or anything prophetic related to the bible? In my opinion, it is irrelevant and also inconclusive and impossible to prove whether any of the purposely ambiguous prophetic language used in the bible has any real significance to current events at all. It is a fruitless pursuit to attempt to map any current events to religious writings, as if any intelligent powerful being would have cryptically sealed important information in an illogical format defying sense and reason and expected imperfect humans to sort out the details or suffer global cataclysms in armageddon. Ridiculous to say the least.
2. Is Iran next for US Attack? That depends on how much financial gain is available for politicans, corporations, lobbyists and the zionists backing them all. If it can be done without intervention and/or opposition from Russia, China, North Korea or anyone else who could possibly thwart the US military, then it is a definite possibility. Iran has oil and a lot of cranky clerics and is the spiritual home of the Shia.
3. Would nuclear weapons be used? I believe the most intelligent approach to avoid being occupied by american capitalists with a zionist agenda is in fact to quickly develop secret nuclear weapons and store them underground where they cannot be located, photgraphed, or attacked from the surface. It is the only deterrent that could keep the greedy coporations away from carving up Iran into contracts and subsidiaries .
4. What would Russia, China do if the US invaded Iran? I believe before any invasion would occur, the US government, its defense industry, and american business with the help of zionists would make sure to carve up pieces of Iran and serve up enough economic opportunity to Russia, China and anyone else to keep them quiet and out of the picture. If I were China, I would refuse to be bought and I would say "no more invasions on this continent". If I were Russia, I would say I get 50% of all the oil action or it's no go! If I were Iran, and I knew it was too late and the invasoion was definitely coming, I would prepare a huge strike against Isreal using everything available.
That's my take.