Here is a cut and paste directly from page 3 of the instructions for the AU undergraduate application. Please make sure to read the very last sentence:
Indicating Your Choice of Major
Please refer to the chart on page 10 of the application for all undergraduate
majors offered. You may also select an intended minor at
this time if you wish. Please note: Preprofessional emphases (e.g.,
prelaw, premed) are not majors. These are advising tracks for students
who plan to enter these fields at the graduate level. If you have an
interest in a preprofessional program, please indicate this in the box
on the application for Career Goal. Many freshmen enter AU unsure
about what degree to pursue. If you are unsure, we encourage you to
apply as “undecided.” You will have approximately two years to
declare a major. Your choice of major will not affect the admissions
decision.
If you still don't believe me, follow this link to find the above quote:
http://american.edu/admissions/pdf/u...pplication.pdf
I don't know what the tour guide was talking about. You simply declare a major at AU. There's no special application or competitive process to endure - you just declare your major. You can declare it on your application, or anytime during your freshman and sophomore years.
PS - Take a deep breath. Your whole life will not be ruined if you don't get into AU. It's a great school, but it's not the be all, end all of colleges.