This is simply factually incorrect. Ireland and Apple lodged the appeal to the ECJ against the ruling in November 2016. Ireland was forced to collect the 13B pending the appeal in December 2017.
The US is not the lowest tax destination - in fact it has a relatively high corporate tax rate. Apple is making their international profits subject to US corporate tax which is why the US is on the side of Ireland and Apple in the appeal.
Sorry, but you completely misunderstand the situation. This is not about moving profit to the US and the US is not the tax haven I'm talking about. Get your USA out of your head and just accept that they don't pay the taxes they are obliged to pay in the EU by evading them.
Putting "sorry" at the start of a comment accusing me of misunderstand the situation doesn't really help here. I've contradicted your claimed sequence of events and of course I googled before writing the post to confirm my memory of the timeline of the EC ruling and the ECJ involvement.
There is no corporate tax evasion here and that is confirmed by reports like this one[1] which makes it clear that offshore Apple (and other US corporation) profits are clearly liable for US corporate tax. The fact that they can defer paying their US corporate tax is due to a quirk of the US tax system and nothing more.
The 3% is a proposed duty/tarif which has nothing to do with how Apple's profits are and were taxed. This is a tax on revenue/sales/imports not on company profits.
The US is not the lowest tax destination - in fact it has a relatively high corporate tax rate. Apple is making their international profits subject to US corporate tax which is why the US is on the side of Ireland and Apple in the appeal.