ARM is a UK company, of course they have the IP. While their highest performance CPU cores have been designed in the US in recent years, they also have design teams in the UK and France. I don't doubt that their European part can adapt an otherwise finished design to a different process.

Intel or AMD IP would need to be stolen somehow. GlobalFoundries might still have some old AMD materials around. Yeah, this does seem really difficult - it would be easier and less risky to run x86 code on ARM if necessary.

Lastly, a factor of 5 or so in computing power does not decide a war.