Out of all the natural tech monopolies, Amazon is the ONLY one that did the opposite of exercising market power. They actually brought fast shipping to the market. A decade ago, you had to pay a crap ton of money to ship things even two days. They forced the incumbents such as Walmart to change. They’re constantly improving e-commerce. Heck they even opened up aws and created an entire industry. Amazon did more to reshape commerce in the US than anyone in the past two decades.
What more does US govt want?