AWS is not digital devices. Digital devices is Kindle, Kindle Fire, Echo/Alexa, etc.
Q4 results [1] say North America produced $1.7bln in operating income, and AWS produced 1.35bln. When Amazon says "North America", I think they mean "North American retail". So while international retail lost almost a billion dollars, I wouldn't say "AWS subsidizes everything".
(Edit: Q4 produces more retail profits than other quarters while AWS is probably steadier, so on an annual basis AWS probably produces a larger part of the operating income. But even so, retail has been operating income positive, so AWS isn't "subsidizing everything".
For the whole year AWS web services made more money than the entire retail operation. 4th quarter is usually good for retailers. That is why you have black friday the day the books become black, aka profitable.
