Joining the Army Rangers?

Hi, i am currently a 16 year old male writing from Sweden. In the future i want to make it all the way into the 75th ranger regiment. I have spoken with the recruiters on goarmy.com and i already know that i first and foremost need a green card. The question is, once i get my green card should i earn my citizenship(Since it is required to get to RIP)through the Army as an infantryman or should i earn it outside and then sign up once i have earned it, which of them would be faster? Any tips whatsoever is appreciated.