You could argue it both ways. The essence of US antitrust is consumer harm. If Amazon were broken up the retail arm might die, and consumers would arguably suf

You could argue it both ways. The essence of US antitrust is consumer harm. If Amazon were broken up the retail arm might die, and consumers would arguably suffer -- they wouldn't receive the subsidies they currently get from AWS, they'd pay more for products and get slower shipping. To argue that Amazon retail consumers would be better off without the subsidies from AWS takes some slightly more complex logic -- that increased Amazon prices would lead to more competition and so lead to lower prices (or better quality). IMO that argument is tenuous. If Amazon, having killed off its competition, were to raise prices I think you'd have an argument, but at the "undercutting" stage I think (IANAL) they're safe.