Even considering all North America + AWS income together, since they paid $1.360B in domestic US income taxes that year (not $162M) the percentage would still be 8.37%, not 1.2%. That's ignoring all foreign taxes and the losses from the International segment. Do you consider a minimum 76% error margin to be "pretty accurate"? I sure don't.
Keep in mind, too, that losses from prior years can be carried forward and deducted from current income. That's part of the reason that there were no taxes paid in the two previous years; the current-year income is only part of the story. This is perfectly reasonable when you consider that $3B in losses one year followed by three years with $1B in annual profits equals no net income for that four-year period. Why should there be any income tax liability when there is no income? The alternative to carrying forward losses would be a refundable tax credit for the years with negative income to offset the taxes collected in profitable years, but that would be very easy to game.
Given the federal corporate tax rate of 21%, the domestic tax numbers work out nicely if we assume approximately 46% of pre-tax income was from the US and the remaining 54% was foreign. Which seems plausible to me, though that is obviously a vast over-simplification and ignores a lot of details. In particular, the distribution of foreign and domestic deductible business expenses may not be the same as the distribution of revenues.
[0] https://www.wsj.com/market-data/quotes/AMZN/financials/annua...