The US doesn't have to change the physical suze of its wire, just give the wire a square millimetre name.
If the US was an isolated country or a net exporter like it was 30 years ago or more, then there would be no need to make any changes.
But, that is no longer the case. American differences cause grief to both sides, in the form of errors and economy.
With the US continuing to export its manufaturing and now engineering base, it becomes even more important to harmonise. It isn't harmonsing for the sake of harmonising, it is harmonising for the sake of safety and economy.
With huge deficits, the rise of the euro against the dollar and the demise of dollar hegemony, the US is either going to have bend some towards harmonising or suffer the consequences of being different when it can no longer afford to be so.
