My mom would never have let me go to a different province by myself when I was a teen,

I agree that it isn't normal for parents to let their kids do stuff like this, but my parents generally don't care. I stayed in Los Angeles for a month last year when I was 16. They didn't have a problem whatsoever with it (it was also during the school year). I will be 18 within 6 months when I plan on going this year. I want to stay out there 3 weeks because I'm probably not going to be out there for another year and it's going to cost me (not my parents) over $500. Originally I was planning on 4 weeks because I was taking a week road trip up to San Fransisco, but that's not happening anymore because my friend got a new job and can't get time off. Neither of my parents cared about the road trip (this was without parents btw) and are still fine if we do that during the 2 weeks. BTW My Mom is fine totally fine with me staying 3 weeks and is on my side.

However, it sounds like his problem is with this girl you will be seeing

I honestly don't think this is it. I was afraid he might say no to that before I asked him, but he didn't seem to care. We've known both families really well for 5 years. He was saying 3 weeks was too long before I mentioned I was staying at her house for a week. He said I should be happy with 3 days staying at the guys house.

He literally said, "That's another reason I don't want you going, you're going to become more liberal than you already are if you go to California". He said this after I disagreed with a crazy conspiracy theory he was explaining to me (UN is one of the evilest things and going to start the one world order...). I also think he doesn't want me moving back to California when I'm older (he hasn't explicitly stated this, but it's pretty obvious), and he probably thinks me going out there to visit friends will make me move. He grew up in CA but strongly dislikes it because it's too liberal and because God is probably going to destroy it very soon. so yeah....

Anyway, all I want from his is a valid reason why it's too long, considering I stayed out there longer when I was younger. I would understand if staying at the girls house was a problem, but I would like to know. The only one he has given me is "school" which was almost immediately conceded. I just don't understand what his problem is considering he was fine totally fine with it when I was younger.

Thanks for replying :)