So is the Moto X, and it seems to me there's a small price delta compared to Samsung's S4 and HTC's One, but not that much. Given that its only final assembly in the USA, and not 100% made in the USA, not sure if being made in the USA would affect costs by that large a factor.

Yeah; for this, certainty, the US issue wouldn't be very relevant. Intel charging OEMs up to 3k for the processors will be more of an issue.