So I started reading book 2 and immediately came across what was bothering me from book one. British slang. Shortly into the book, the main characters father asks for a spanned, and made a comment that everyone knows what a spanned is (or something like that). No one in North America says spanner, they say wrench. Spanner is a UK slang, particularly from Ireland. Unless the author comes outright and states the character is from the UK, it takes all immersion out as Americans and Canadians do not use those terms, and suggesting the person talking that way is a New Yorker of all regions, not only will not speak that way, most likely would have no idea what you mean.
Someone to edit out these oversights seems like it should be a high priority. That, or say early on that the family immigrated to the US early on, from the UK, to explain the strange word choices.
I have, a number of times, seen people from the UK mocked for using these words. Growing up next to a British family gave me some insight. Torch instead of flashlight, lift instead of elevator, mates instead of friends/buddies/etc should be mocked by other teens if it was being realistic, even if good naturedly. It’s a big, glaring suggestion that this is not an American speaking.