Re: "There's a long history of API's being *outside* of the bounds of copyright"
If you insist:
17 U.S. Code § 102.Subject matter of copyright: In general ( https://www.law.cornell.edu/uscode/text/17/102#b ):
pay particular attention to section b:
"(b)In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work."
An API is a just such a 'system or method of operation'.
Then there's Baker v Shelden ( https://en.wikipedia.org/wiki/Baker_v._Selden ) back in 1879, where a system of accounting was ruled unprotectable by copyright. This came down from no less than the Supreme Court. His _book_ (a particular expression of the system) was copyrightable, but the system wasn't.
Then there's Bikram's Yoga College of India v. Evolution Yoga, LLC ( https://www.eff.org/files/2015/10/09/yoga-copyright-opinion-ca9_0.pdf ) in which the ninth circuit court held in 2015 that the sequence of poses was not the proper subject of copyright. This decision is important in two ways, first it provides a plethora of references to the various decisions underlying why an API isn't copyrightable including the previously mentioned Baker v Shelden. Second, the Federal court was _supposed_ to apply the rulings of the court where the case originated, which in this instance was the ninth circuit. Instead they chose to ignore precedence and rule that APIs are protectable by copyright.
As for your contention that AMD 'had a license' from Intel, that was for the use of their patents, not any copyrights (spoiler, there weren't any).
It's funny that you mention AWS. Do you know that Oracle has implemented Amazon's S3 API without permission (which is perfectly legal) ( https://arstechnica.com/tech-policy/2020/01/oracle-copied-amazons-api-was-that-copyright-infringement/ )? Oracle is claiming that it's OK because the Amazon SDK is licensed under the Apache license. But that's the *SDK* _not_ the API. Java's SE SDK was licensed under the GPL, but Oracle is arguing that license only apply's to the SDK, not the API.