I know it can be galling brickhistory to have foreigners disparage your national industry/products, but even the most ardent Americanophile (and I am one myself) has to concede that the A330 MRTT is a superior product in every regard to the KC-46A.
I'm usually able to see the relative merits in competing platforms, noting how the capabilities of one might suit a particular user while the capabilities of another might suit a different one, but with the MRTT vs KC-46A debate I cannot find a single criteria (except political with regard to KC-X) which favours the latter - there is simply no competition when it comes down to platform performance.
That said, yes there are developmental problems with all aircraft (MRTT boom detachments anyone), but the KC-46A's deficiencies go beyond the here-and-now problems that the programme might be experiencing.
And don't forget also, the KC-45 was to be built in Alabama, and so would have been a US-built product.