I think the two major differences between the United States and Denmark are:
Getting used to a walkable city
If you’re not biking, you’re walking. There are buses and trains to help when you’re going long distances but for the most part you’re walking. You learn your way around fairly quickly and personally I loved walking more than the public transportation because I got to see more of what’s around me. I’d always leave the house with plenty of time so if I passed by a store or something that looked interesting i’d have plenty of time to take a look. Sometimes I would pass by a park and take a detour through there. The parks in copenhagen are my favorite because they’re all huge and alive and most of them have lake or pond in the middle. I’m from Chicago which is very much a concrete desert. There’s not much parks and the parks we do have are no where near the ones in Copenhagen. You really feel like you transported to a different place with all the nature.
It’s silent pretty much everywhere
The trains and busses have silent zones and even when you’re not in a silent zone it’s still silent. A clear giveaway that you’re American is talking on the bus or making noise. Coming back to America I got very overwhelmed very fast by all the noises around me and how loud everyone was. Denmark in general is very tranquil and silent. I think just respecting the silence around you is a very huge part of understanding the culture. Normally when you’re going home from going out on the weekends that’s when the public transportation gets a little rowdy but other than that expect silence.
I personally loved the quietness and the walking that came with Denmark. I felt like it allowed me to connect more with what’s around me. If the silence really isn’t your thing that’s totally fine, just make sure your airpods are charged.