Amazon has past the point where vertical integration questions should be raised and a break up should be considered for the public interest - not pursuing it for them (or Walmart, or Google, or many other too-large-to-fail corporations) is another form of assistance the government offers them.
The US is not a free market and participates in private industry subsidization both with and against the public interest but, I agree, it's no where near China's levels - to keep it from getting to those levels we need to acknowledge how bad it has already gotten.
Chinese nationals are the largest foreign group of investors in US commercial and residential real estate. They have plenty of access. The success and scale of the Belt and Road Initiative directly shows just how vast the control extends.
In China the government appears to clearly control the corporations (while there are some highly influential corporations that, through their economic power, have essentially become moves and shakers in the government) in America corporations control the government (while there are a lot of former politicians who end up sneaking off into highly paid do-nothing positions for their help during their tenure in elected office). These things are different, and America is absolutely a more free place, but it isn't an absolutely free place.