There is no country on the planet that is 100% capitalist or 100% socialist. They're blends. What I see as the biggest problem of the United States economy is corporate monopoly, like (as you pointed out) the ironically named Amazon. It's a problem we've seen over and over throughout our history. Corporate monopolies create oligarchs who control our government in order to serve their own interests. I think we need a Constitutional amendment that prohibits monopolistic behavior by corporations, but that would be hard, considering our politicians are bought and paid for.