What's the point of a google coin?
If it's centralized and controlled by them, that takes away a huge benefit of bitcoin so why would anyone switch over to google?
So de-centralisation is the most important property of bitcoin? People will transfer to any cryptocoin that's more convenient, if that's Googlecoin, they will go there. de-centralisation is only an issue for certain political aims.
Considering the main innovation within bitcoin is the fact that it solves the problem of how to get a decentralised network to agree on a certain thing, it's strange you would even ask this.
What would be the difference between 'Googlecoin' and Visa?