I don't know how it works in USA, but (in my experience) in Europe you're rarely stopped by customs officers, unless you are bringing loads of luggage or big boxed articles outside suitcases. I was never inspected.
At that specific time last year, I transferred in UK before travelling to my country. In that situation, I didn't pass through customs at the first airport, and when I arrived to the second airport I was coming from an EU airport in which case you never pass through customs (AFAIK).
Another thing you could do is to carry the purchased articles outside their boxes (but still in suitcases), which makes it easier to convince them you're just taking stuff back and forth. They might ask you for receipts though...
PS: I don't think the above advice could ever get you into trouble, but the usual disclaimer applies. I'm not a lawyer or anything of the sort.
My Mario Kart Wii friend code: 2707-1866-0957
