I live in USA, and whenever I visit another person's home, I ask them what they would like me to do with my shoes. I think when I visit someone, it feels uncomfortable to take off shoes, so I will only do it if they tell me where to put them. If they ask confused or seem like they don't care, I will still wear them. Whenever someone visits my home, I let them know when they arrive they are free to take off their shoes if they would like. I understand some people don't feel comfortable taking off shoes in someone else's house, so I usually let them wear it if they want. But if it is rainy or snowy I usually ask them to please take it off. I take them off in my own house.
I think it's because the feet become "exposed," and even through socks, some people here think feet are "gross." I hear lots of people complain about how gross feet are and how they hate things like sandals because they don't want to see feet. Once I overheard someone talking about me when I took my shoe off outside at a park to remove a rock from it... they said it was so gross I would just show my foot in public. So I think it is a culture where sometimes people are very bothered by seeing a foot, idk. Very strange to me. I don't mind feet at all, but it makes me self-conscious and uncomfortable to take my shoes off in someone's house because of this.