I was in Japan, bought a U.S. ipad and logged into my U.S. account and was happily downloading stuff. It doesn't where you are at, it matters what country your itunes account is linked to.
Also with regards to Amazon. I could log into my U.S. Amazon account and order stuff all the time. I am a Marine so I had a "U.S." address to have stuff mailed to and if an item couldn't be shipped FPO, AP I would use APO.com. I accessed Amazon from my off-base residence. On a side note, I miss it over there, 100 megabit fiber to the home for about $60 dollars a month.