If you’ve visited Iran, Iraq, Sudan or Syria on or after 1 March 2011, then you’ll no longer be able to use the USA Visa Waiver Program. You’ll need to apply for a visa through the regular process at a USA embassy or consulate. And if you already have a valid Electronic System for Travel Authorizations (ESTA), it will get revoked.
The Department of Foreign Affairs and Trade has recently updated the Smart Traveller Website which advises more about these changes.
If these changes impact you, you should read more on the US Customs and Border Protection Website.