My cousin wants to apply for Aerospace engineering here in the US. Which university would be the best and easy one for him to get into? Any ideas.....Or should he apply for another major first and change it to aerospace engineering later on? 

This might sound a little bit bitter, you dont have to take my advice.
That said, here is my advice for your cousin, my own cousin and anyone else who might care to listen.

DO NOT think of coming over or applying for a visa until you get a scholarship of 75% or above. If your I20 has a 4 digit number in yearly cost, you will end up with "ghanta hanne" and community college.
my advice is work hard for your board exams and SAT, get good scores and apply to at least 10 schools yourself (not through consultancy, this will give you a lot of knowledge about education here and about the school itself which will help you excel).