I cannot speak for the English because that is not my culture or genetic make up; and honestly I know practically nothing of England.
Cultural appropriation is taking stereotyped pieces, like you have in your ask “tipis and smoking pipes” and using them when you have no genetic or culture tie to those pieces.
I have some Hungarian blood, for example, but I know nothing about Hungary, their customs, culture, etc; so if I wore one of their cultural pieces of clothing, or participated in a reenactment of one of their cultural practices I would be committed cultural appropriation. I know nothing about them so why attempt to copy them? Copying stereotypes is not a form of flattery.
You asked how dressing up like a race could be comical or racist; I will attempt to answer this the best I can, even though there are more well written articles on the subject.
You asked if it is cultural appropriation for non-natives to use tipis, while I cannot speak for all Native peoples I will answer for my personal opinion, yes I believe it is cultural appropriation. I grew up in a tipi, my friends and family did as well. When I see people use copies of my home as a camping tent they are like the unwanted tourist. “Let’s go see what being an Indian is like and tomorrow go back to our two story house”. They are mocking the way some people grew up and putting it on for fun and taking it off again. We are not a costume.
The way I was raised, I was told that if I ever needed help I should go to person wearing a warbonnet. Imagine being a child, needing help, and going up to some white guy wearing a costume warbonnet. It is highly offensive for non-natives to wear warbonnets. But all forms of “Native American” costumes are wrong too. When I went to public school every fall the kids would dress up as “Indians”. Can you imagine how it felt to look at a bunch of kids mocking your people?
These racist costumes do reduce my race into something comical.
How is it not comical to dress up as a race?