Americans can easily travel almost anywhere — except here
https://edition.cnn.com/travel/article/americans-hardest-countries-to-visit/index.html
Iran is hated by the US government so heavily that not only Americans but also citizens in allies are restricted from getting in Iran in some cases. For example, if Japanese citizen has a record of visiting Iran, he/she will be barred from the United States.
So, people in allies of the United States, please be careful.
