I once tried giving Microsoft points to a friend who lives in Canada but he couldn't redeem them because they were purchased in America.
If you got the points in America and are trying to use them in another country I don't think it normally lets you.
I tried downloading the Heroic map pack from Halo 3 in Ireland and it wouldn't let me but when I got back home, America, I was able to download it no problem.
Point cards are tied to specific regions due to the difference in currency. You friend could have got around that by making an alternate, US account on his console. I'm Canadian and have a US account as well as a Canadian account. I did it because I found it was often cheaper to buy US point cards on ebay, and other sites than to buy Canadian cards at retail.
Some XBL content is region-locked, but most of it isn't. Halo and Call of Duty map packs, all Games on Demand content, and Dead Rising: Case Zero are the only region-locked items I'm aware of it.