As usual this is excellent info from
@StPaulDad .
First assignments are just that and have very little to do with major and almost everything to do with your class rank. Aviation and Cyber have in person interviews, but other than that class rank rules the day for now. When I watched Billet night last year, I believe only one of the 6 or 7 that went to Cyber was a actual Cyber major as an example. But your degree choice does point you to possible second and third assignments. All engineering majors will take the Fundamentals of Engineering (FE) exam prior to graduating beginning their 4 year journey to become a Professional Engineer (PE) if so inclined. Some of the traditional undersubscribed majors historically have been Electrical Engineering (EE) and Operations Research and Data Analytics (ORDA), but they are pretty demanding with a lot of math and computer programming. Your undergrad degree will also have a bearing on what grad school options are available if you stay past your 5 year commitment or if you get out. For example it is challenging to attend a Graduate Engineering degree with a non-engineering BS.
All that said, choice of major is one of the few decisions you can make as an applicant to the academy and you should be true to yourself, your interests, and your abilities that way you have the best chance of enjoying your Academy time and performing well which will lead to a higher GPA and class rank which will then give you the best chance of getting the first assignment of your choice to begin your career.
Best of luck!