I really dont get this excuse: how the hell would this situation be possible ? Do stores in the US just let you exchange/return itens without a receipt?
Yes, they do. Many stores have no-receipt return policies for in-store credit only. And stores that don't have a no-receipt policy can generally be talked into returning for store credit or equal-cost exchanges if you complain to customer service enough.
And then there's the trade-in aspect, especially for electronics and video games. Nearly everywhere that has any used game sales, accepts trade-ins for store credit. And those are much easier to sneak past. You get like $0.25 - $0.50 a game sometimes, but that adds up when you pull 100 games out of a dumpster for free.