One thing I can say I have noticed as universal in all types of American churches is that when attending, you wear your "Sunday best". Meaning that church goers would dress up for God, usually in something a step above their daily garb. For men this meant button up shirts, maybe ties and a casual suit jacket. For women and girls it usually meant a conservative dress or skirt. Whenever I attended church with friends or family, I was always reminded to dress nicely and respectively.
Now I thought this was a religion wide thing. The thought never crossed my mind that dressing in your "Sunday Best" for church was actually a very American tradition. I have gone to several Catholic services in England, and I am always astounded by how casual the dress code is. At first I thought it might be just that specific church, but then it was explained to me that "Sunday Best" was actually a very American way of thinking. And in England, it didn't matter what you wore, but that you were attending church.
So while I would be shocked to see a teen wearing a graphic tee at a service in America, in the UK it is more acceptable. T-shirts, jeans, shorts, and everyday wear are normal and completely allowable. This is yet another striking difference between the USA and UK. A rather surprising one I might add, as many of the American churches have British origins. But as is common knowledge in America, the first settlers moved to flee religious persecution. So perhaps the original colonialists and later descendants thought it was more respectful to dress up every time they went to the house of God.
I appreciate and enjoy the more relaxed mentality towards clothing in church in England. However I don't think I will ever be able to break my lifelong habit of dressing with more care when on Sunday.