They certainly should. Whether or not they do today is irrelevant. It's logical that they should. It's in the interest of your users to host near them. Focus on your users, not whatever SEO hacks work today. What serves your users best is sure to eventually become search-engine criteria.
It's a bit of a complicated issue, though. If you are, say, a European manufacturer, selling European goods to the US, I would think where you host would be less of a factor than for somebody selling US books to the US. But still a factor - a European company with a U.S.-based web site is catering to their US customers more than one with only a European-based site.
I'm curious, though, why you want to host in the EU? You say the "books are targeted to the USA". Are your target customers in the US? Or are you marketing books intended for the US market in the EU?
If it's the former, why on earth do you want to host in in the EU?
If it's the latter, just make sure that it's clear that you are marketing US books to customers in the EU. The search engines should pick-up on that and give you a boost with EU customers.
Bottom line, focus on what is best for your users/customers and you've already got most SEO under control.