I don't think AMEX has any formal interview processes.
It totally depends on the unit you are applying for.
For me, the first round is a phone screen, then a group phone interview, then a hiring manager interview.
Technical questions, behavioral questions.
The following metrics were computed from 4 interview experiences for the American Express Senior Engineer role in United States.
American Express's interview process for their Senior Engineer roles in the United States is incredibly easy as the vast majority of engineers get an offer after going through it.
Candidates reported having very good feelings for American Express's Senior Engineer interview process in United States.