It's worth noting here that USTravelDocs (which is an official US Government resource) asks two questions on their FAQ about whether you can visit the US to look for work and attend interviews:
Can I go to the United States to find a job and then apply for the E-3 visa from there?
“In advance of applying for an E3 visa you may travel to the United States to search for a job or attend an interview. However, you cannot apply for the actual visa from within the United States. All visa applicants must appear at a U.S. Consulate or Embassy abroad to apply.”
And
Can I travel to the United States on the Visa Waiver Program to find a job or attend interviews and then apply for the E-3 visa once I return to Australia?
“Yes, you can travel on the Visa Waiver Program (VWP) if you meet the requirements (please see our page on the Visa Waiver Program). If you do not meet the VWP requirements, you may be eligible to travel on the B-1/B-2 Combined Visa for Business or Pleasure.
“You must leave the United States before applying for your E-3 visa.”
For more information about work visas in the United States, see our introduction here.