This is my peeve as well. I rant in every semi-relevant thread here that they should glue some washers in them to make the weight right. I get that actual liquids would be a hassle for production realities, but the weight is obviously wrong in them too.
Yah Americans tend not to take their shoes off indoors which I found weird and disturbing even after 25 years of living there. It always felt rude to me, even though I knew it isn’t considered so there.