I am willing to bet Facebook did not pay Irish taxes on US income, but failed to pay US tax on non-us income, which is a different thing, as the US have signed

I am willing to bet Facebook did not pay Irish taxes on US income, but failed to pay US tax on non-us income, which is a different thing, as the US have signed treaties with the EU preventing them from taxing revenues that an company have already paid taxes on in Europe, so the IRS suing Facebook from headquartering in Ireland would be an severe treaty violation and is likely not what is happening in the real world despite it being an obvious angle for fox to try and push to their audience. The problem with Facebook/Google taxation(the EU is even less happy about it) is that is that by moving the money through Ireland(who dont tax corporate transaction, only Irish revenue) the profits end up in limbo somewhere in the Atlantic where nobody gets to claim taxes on them. It is essentially the reverse of what the EU is suing apple over as apple insists that their profits is taxable in the US despite not paying tax on their IP related profits in California.