Major companies have the power to bankrupt states. They do this within the US, and they do it with countries. Once the state is in debt, it pawns its assets and outsources its services to corporations; and it ties its budget to creditors who lend conditionally. In other words, they surrender their sovereignty and subordinate themselves to private sector power. You did not elect those CEOs and shareholders, but they exert control over your government, and you cannot vote them out of power.
If we do not develop mechanisms for the democratisation of corporate power, democracy as a political concept will cease to exist in society