The idea that IF Iran got nuclear weapons, other countries like Turkey or Saudi Arabia getting them would build them too and start an arms race is as absurd as the fear once N. Korea got nukes, South Korea and Japan would build them too as a deterant. It's all merely unbased speculation and hype.
The only real reason the American public fears Iran is because the corporate media sources most of the trust and watch say it it is. Most Americans work during the week days to come home to corporate news sources telling them about the latest threatening remarks Iran has made to the West, supposed terror involvement in Iraq, Israel, the United States, or Afghanistan. Too a story about the latest hardware Iran bought from Russia is next without stating the purpose it was bought for or where it is going. The newspaper through the AP recirculates what they say to increase their readers. On Saturday or on their day off during the weekdays, most readers will being reading books about future speculation, television shows that deal with the theme, reruns of old specials on the History, Discovery, or National Geographic Channels dealing with the topic or pseudo science, especially Bible prophecy. Saturday often brings the video games sponsoring it or ads by the US military on during violent these times to get these impressionable minds into the idea too. By Sunday, most Americans will have at some point gone to church or talked to someone who went and been warned about the End Times coming, the dangers some vague source in Israel said or was quoted from a cable network by the preacher warned about Iran's nuclear program, usually FOX, and they will think about it and believe it more. Some will often give them a DVD or a book they bought promoting this idea and the need to protect Israel from a nuclear holocaust by Iran. Most of the few televangelist shows available on TV will deal with end times topics the entire broadcast and sell products endorsing the idea too.
Only a few corporations control most of the television networks, magazines, and major newspapers in the United States. Video games draw from major events, often with a corporate owner not on the label like Disney or Fox and make games like Call of Duty, Battlefield, Tom Clancy's End War and more to satisfy their fans, promote the dangers of war in the Middle East while too desensitizing them to violence.
It's already common sense that the highly-religious, millionaire, corporate investing members of Congress manipulate war for profit and have many deals with special interests from a variety of backgrounds. Religious leaders have similar relationships, but especially in the Republican Party. The entire system promotes a pro-war agenda because it stands from gaining profit, increased viewership, and political control from a war in Iran or the fear there is going to be one and they have mined the controlled routines of Americans for decades with it.