I reject the idea that something that originated in one society cannot become another society’s culture. It morphs and changes, and is reinforced by the society until it becomes a part of their culture, too. Surely you would not say that tomato-based foods aren’t part of Italian culture just because they came from the new world?
What they make of it in Italy is vastly different from what was done with it in the Americas, so no, but if it’s the same practice that was brought over through migration and most people started doing it, can it really be considered original to the culture of the country? I personally don’t think so…
Light beer as it’s known today is US culture (nothing in common with small beer), but as I mentioned, trick or treating is just a tradition that came as is from elsewhere and was adopted by the locals.
Does culture have to be original?
Also, having looked into the trick or treating thing a bit: Canada invented the phrase “trick or treat”, and America has variations such as trunk-or-treating. Modern trick or treating doesn’t involve performing at the door. Some of these innovations (ie. the phrase “trick or treat”) have even propagated back to the originating countries. I think a binary view on this is too restrictive and unrepresentative of the reality of the situation. The tradition is still very similar to what it was, yes, but it changes over time.