Iran is slowly getting out of the embargo sphere, trade with and investments in the country are on a steady way up.
Travelers to the USA need to take the following into account:
After having traveled to Iran, there’s no possibility for making use of the US Visa Waiver Program (ESTA) for travel to the USA anymore; the traveler will be refused entry or even boarding.
A subsequent trip to the US requires the issuance of a visitor’s visa (B-1/2), issued by a US Embassy or Consulate General.
Foregoing is also applicable to "US travelers", after having visited Iraq, Libya, Somalia, Sudan, Syria or Yemen.