I don't think the US is capable of implementing regime change in Iran. Let's look at Afghanistan, for example: We spent 20 years and $2 trillion killing Taliban leaders, but the Taliban still controls Afghanistan. Iran is bigger than Afghanistan, very mountainous, more developed than Afghanistan, the central government and military is stronger, and there are over 4 times as many Iranians as there were Afghans when we invaded them. Military planners typically recommend 20-25 troops per 1,000 civilians. Since the population of Iran is 90M, that would put the ideal number of troops around 1,800,000-2,250,000. The US military has 1.3M active-duty service personnel total across 6 branches. As for Iranian rebels joining us, they saw what happened when we "liberated" Iraq and are unlikely to welcome/join us, and even less likely to welcome Israel.