The Americans also built an experimental Israeli reactor. Israel had lots of help developing nuclear power, but, Israel went on to build nuclear weapons. In the case of Iran, at least they are paying their own way. If they also build nuclear bombs, they will only achieve parity with Israel. Actually, it will take a long time for Iran to equal the nuclear arsenal which Israel has built.
from the article: Top U.S. official: Military strike on Iran was never 'off the table'