Iran responded strongly to the US’ new strategy, and the EU also voiced different opinions.
What are Iran’s retaliatory options? What can the EU do to maintain the deal and will China do the same?
Iran can potentially restart development of a nuclear program, including operation of nuclear reactors and preparation of enriched uranium. This would invite the USA to launch military strikes to disable the nuclear program. Iran may gamble that the USA would not follow through on threats to do so.
Iran may utilize foreign terrorists groups funded by Iran to strike USA forces with retaliatory bombings, or may simply increase presence of Iran funded groups in Syria.
Iran may use influence with Hezbollah and other militant groups to threaten or attach Israel, a chief ally of USA in middle east.
Europe and China will seek to meet Iran’s demands for maintenance of the deal. Both can do so if they wish from a policy perspective, but this would not be without consequence from USA. Trump administration has already issued severe penalty against Chinese company ZTE for violating USA sanctions. European and Chinese companies will open themselves up to similar sanctions. Many
European companies have already started withdrawing from business with Iran.
Iran may also withdraw from the Nuclear Non-Proliferation Treaty which it is a member of.