This is very specific to the culture. I wasn't allowed to play with guns, as a child growing up in the US. But I wanted guns and I was fascinated by them, and I enjoyed learning to shoot real ones eventually. So I assumed ALL kids were the same.
They're not. My children, growing up in central urban Canada, have never been interested in guns. None of their friends have toy guns. There's no cap guns. No pointing fingers, no shooty noises, none of the stuff I remember from when I was a kid! Nobody around here bans guns, because the kids just don't care.
My children played with swords an awful lot, though. Sticks got swung at each other like hockey players in a brawl. And bows and arrows definitely interested them. Snowballs, with ice packed in the center! So yes - the aggressive play still exists. The weapons are just different. And fwiw, I doubt urban Canadian kids are MORE violent than urban American kids, just because they don't play with guns.
(I won't hazard a guess as to how Canadian kids play on the west coast, or the prairies, or in rural areas - I'm sure there's regional differences!)
Not all kids in the US play with guns either

. So, rather than make an issue or feel bad; I purchased a regular gift for the girl, that my ds was friends with (I normally spend about $20 and that is about what I spent on her) and I only purchased a small gift for the boy I didn't know (under $10). These are really nice people and I know they were not trying to be inconsiderate by basically asking for a gift for both kids; but personally I think just buying for the kid that your child is in class with is the appropriate thing to do....