Ah, but you forget the age old problem of government regulation:
Regulatory capture
I guarantee if you got such a law passed, Google, Apple, and Microsoft will be the ones actually writing the law, and running whatever organization is supposed to enforce it.
And I guarantee they will make it extremely hard to comply with simply to drive up costs to competitors.
It won't actually do anything useful, or there will be one good aspect left in as a fig leaf. It will, effectively, be a very expensive to comply with pile of empty words.
Regulatory capture
I guarantee if you got such a law passed, Google, Apple, and Microsoft will be the ones actually writing the law, and running whatever organization is supposed to enforce it.
And I guarantee they will make it extremely hard to comply with simply to drive up costs to competitors.
It won't actually do anything useful, or there will be one good aspect left in as a fig leaf. It will, effectively, be a very expensive to comply with pile of empty words.