So, I got a few PM's about this, glad to see there are legit music/movie purchasers out there other than me lol. I spent about an hour figuring out the whole process, so might as well share this with everyone.
So, why a US Account? The US iTunes store has content that's not available in the Canadian store. Not just music and movies... TV shows, iPod or iPhone apps, everything is better in the US store. There's even more free stuff to keep you busy. So even if you don't plan on buying anything, it's nice to run off the US account for the free stuff. If you're buying stuff, music store has a lot of older hit albums that for some reason isn't found in Canada, movie store has way more new HD stuff for rent, and TV show store just isn't comparable. It's like a completely new store! The Canadian store has CBC shows, and that's about it lol. The US store has *every* TV show imaginable.
Alright, now that's out of the way, first thing you need is a US iTunes gift card. I'm assuming you guys don't have US credit cards with US address. You can buy these off ebay, just search for iTunes US and you'll find tons of classified hits for them. If you want to access just the free stuff, buy the cheapest card. I bought a $60US card for $70. The sellers email these out fast, within the hour.
Once you get your gift card redeem code, open up iTunes. If you're already signed in, go to the Store menu and choose sign out. Next, you have to switch to the US store. At the bottom of the store "home", change My Store to the US store. Once the US store pops up, click Redeem, and enter your code. It'll ask you to create a new account or log in. At this point, create a new account with a fake Montana address (Montana has 0% tax, so use Montana otherwise you'll get taxed on each purchase). Just google up something from Montana and make up an address. Once the process is complete, you'll be logged into your new US account with the $ from your gift card, and you're good to go! In the future, just buy the cards off ebay (I'm going to buy them next time I'm in the US) to recharge my account.
For iPhone, the next time you sync, you'll be setup on the US account on the iphone. You may need to do a hard reboot of the phone to fully access the store (hold down power button to turn it off then turn it back on).
For AppleTV, go to your settings and sign out. Change the location to the US, then sign in with the US account. Simple as that.
Now that you have your US account, you may notice that downloads from the US store are slow compared to the Canadian store. REALLY slow. It's not noticable for music, but for movies and TV shows, it took an 70 minutes to download a 44 minute TV episode. I started diagnosing the problem, and realized that Apple (who uses Akamai for content distribution) will use a different cluster of servers for US. The bandwidth to Canada is just horrible, so downloads are just untolerable.
So, we have to trick Akamai to give us IPs for servers in the US, and for the techies, Akamai guesses your location based on the DNS server you're using. Thankfully, there are free US DNS servers we can use. After testing a few, the best are the Level 3 DNS servers. I used 4.2.2.1 and 4.2.2.2 and now get 11mbps downloads off the apple servers because it thinks I'm in Colorado with lots of bandwidth.
I wouldn't bother changing this for iPhone (it wont work well everywhere, besides you don't need the speed on it), but definately change it on AppleTV, as well as the computer that you have iTunes on. Your downloads will now be twice as fast as the Canadian store too!
That's it. Enjoy the US store!