Two of the most isolated parts of the world that would probably suit you are Siberia and Northern Canada. But be warned, it can be savagely cold in winter and unbearable in the Summer due to mosquito's. You'll also have bears to contend with in both countries.
Your chances of survival without the correct training and kit are minimal. Chris McCandless's story is a classic case - and he was no virgin adventurer (he starved to death after mistakenly eating the wrong plant that made him ill). Take a few trial periods in a wilderness region in both summer & winter. Learn to navigate & traverse the landscape. Practice your survival skills & practice your building skills. You'll need to think long & hard on what kit you need (and I mean REALLY need), and what skills you'll need to master - you'll need to know how to catch (or harvest) and preserve food. You'll need to know medical skills. You'll need construction, woodworking, leather working & primitive bushcraft. You'll need to know what type of land you're building on - you don't want to live in a swamp during the summer & under threat of avalanche during the winter.
You're 18 years old which is the same as me, I understand entirely where you're coming from because I think exactly the same. I hate the whole control system, I go to college and also have a job, I love my job but I hate the whole idea of 'civilisation' when it isn't really civilised at all. You're still young so as much as you think you do (like myself) you really don't have a clue about the way the world works yet. My advice would be to focus on your college and give it your all for the duration of your course, as much as we like to think we can it's not as easy as it sounds to up sticks and abandon civilisation. Get good grades so you have something to fall back on and consider everything carefully, living in the wilderness takes a lot of effort. Also like you said you'll return one day so you'll need good qualifications if you want to survive.
Learn to sail, buy an old yacht and do it up, live aboard, cruise the world, any time some person or place bothers you, haul up your anchor and move on. It is definitely still possible to do that, and there are a lot of people doing it right now as we speak.
Well it's one thing to actually dream of it and another to actually do it. That guy from Into the Wild just did it. He took the plunge head first without looking. It did get him killed though. If I were you I would spend a year trying to learn as much as I can, then get a backpack and go. I don't really know what else to tell you.
Do it. Civilization really does suck.