As a Dane I’d guess they didn’t realize Americans use it as a greating and so assumed you to be initiating a conversation unrelated to ordering, possibly with bad intentions.

It would be a little like starting the conversation with a “how is your mother”, it would signal way more familiarity than was had, come way out of left field and be generally unwanted when you are working if you don’t have time to stop for the conversation that would ensue.

Don’t get me wrong, I don’t think you did anything wrong necessarily, it’s just a cultural difference that likely causes misunderstandings if none of the parties are aware of it. I’d liken it to a Eurpean going to a restaurant in the US, not tipping anything and how both parties may feel the other party to be rude after the fact if the server let their dissatisfaction show.

I could of course be wrong and they may just have been an ass, plenty of those in tourist heavy areas for sure. Just something to consider if it could have been the case.