Actually no I don't think it would be a serious threat to the US. Israel, most definitely. It would take missile launch capabilities that Iraq does not have nor will they receive while we have inspectors in Iraq. It's not that easy to make a nuclear bomb and even harder to make a small one.
The real nub of the question is - Do you think people in Iraq, Pakistan, India, Jordan, Israel, or Saudi Arabia have a right to defend themselves and be able to develop nuclear weapons?