I don't necessarily think you are too young. Especially if you don't have kids.
I do feel in your case one year is too soon. I think the younger you are, the longer you should take in making the decision.
I also understand your friends' concerns about moving to Europe. As a person who grew up abroad, I can tell you moving is one of the hardest things I have ever done in my life. Whether it was moving across the world or across the country.
I moved across the world with my family and it sucked. There was so much to adjust to, so many people I was away from, I was depressed a lot.
I moved across the country with DH and it was a HUGE struggle, financially, mentally, emotionally...it has been so difficult.
We have a solid relationship though, we dated for over four years, engaged for one, had met and stayed with each other's families, had premarital counseling...you name it, we did it.
Perhaps your friends are concerned that you will be making 2 huge changes in life, and without support from other people close by. Europe is his playing ground and he has all sorts of support built there, and you probably don't.
I say I don't think you are too young. Just make sure you are mature, get counseling, and in as much as you don't want to hear "you are too young," really open up and ask people to give you SOLID reasons why they think you care unprepared.
You are "too young" is just a broad term that encompasses several things such as:
maturity
finances
decision-making
committment
etc.
Let them give you specific reasons why they think you are too young and evaluate the reasons. People told me I was too young because I hadn't finished grad school and would miss single life.
I'm married, and still finishing grad school, and I don't miss clubbing or other things they think I would do as "single." Except maybe the option to go wherever I want for the holidays, now we have to split them.