They’re not. Why are you making that assumption? The US is saying that in order to access the US market they have to divest. They’re free to sell at a fair market price - including to European buyers. They can also choose not to and leave the US market and keep operating elsewhere. They can also just sell the US business and keep everything else the way it is.
To be fair being legally mandated to sell significantly reduces that “free market price”. Technically it’s certainly not “free” anymore..