I'm not very clear on the border issue with such a new car.
As for registering (In CA, I assume). I brought a car down from Canada and registered it in California. There are quite a few hoops to jump through, but it's not too difficult.
First, you'll need to make sure the title is clear in Canada. IE, no liens, all the registration is in your brother's name, etc...
First (b)

: Go to your local department of motor vehicles in California to get your license and get the package to change registration.
Second, you'll need a letter from the dealership that the car doesn't have any recalls on it (easy enough to do - IIRC, you just need to physically go to the dealership with the VIN).
Third, you need the car to be inspected by the California Highway Patrol. This is the hardest part because they are so heavily booked. Also, you can't go to any CHP station, but rather the one designated for you address. You may want to call the CA Dept. of Motor Vehicles to see if there's a specific form you need to take with you. Make the appointment early though - very booked up!
Fourth, you need to get the car smog tested. Not difficult. Pay attention to newpapers/junk mail for coupons - saves you 25-50%.
Fifth, once you have all the above assembled, you need to mail it all (make copies for yourself!) to the CA Dept. of Motor Vehicles in Sacramento along with your AB (or Canadian) license plate.
Driver tests are pretty straight forward, but if you have a crack or ding in the windshield, consider getting it fixed before hand... especially if its remotely close to your field of vision (my own experience).
RE bringing the car over the border: it can depend on what visa your brother is entering the country on. If it's an F-1 (student), the agents don't really care because they assume you're leaving at the end of study. Otherwise, I'm not very sure.
IIRC, it's more the number or steps and length of time to get it done over the difficulty of any one step.
Let me know if I can be of any other assistance.