There was no interview process, ever. The US Army Human Resources Command, Ft. Knox, KY runs everything, including job placement, human capital management and advising officers seeking positions. You have to go through HRC so don't bother trying to go around them.
Depends on the role you're planning to fill, whether you're an officer candidate, direct commission officer, enlisting as a Soldier, etc. As a direct commission officer, I met with various recruiters and other officers but it was less an interview and more an assessment of physical and mental capacity.
Intense healthy physical, followed by a panel and screened interviews with upper echelon officers to determine if I was capable of being an Officer in the US Army. I would classify this difficulty as intermediate as it required being attentive and ability to think critically, quickly.