Prom - URGENT

So i can either go to prom or go to america for a month and see my cousin(i havent seen her in 7 years) i dont know what to pick because havent got a dress yet and prom is in 3 weeks.
Is prom really worth is because i feel like if i dont go ill feel left out as people will be going to after parties ect and posting on their stories,prom is only once in my life but its also only 3 hours.
What would you guys do?