Processes, whether they're made up of abstract concepts or not are patentable[0]:
"Processes are patentable under the U.S. Patent Act if they meet certain criteria. A process patent is a form of utility patent that covers methods of changing the functionality or characteristics of a material during a particular use. The patent-holder is granted exclusive protections and rights to that process for 20 years.
When one patents a business method or, in some cases, a computer program, this is a form of patenting a process. It's now possible to patent subscription-based services, targeted advertising networks, online auction sites, portal sites, email systems, and even discussion forums.
As our society has evolved, intellectual property (IP) issues have evolved along with it. What constitutes IP these days is so much more than the newest machine or physical invention. Today we have genetically modified seeds, new strands of DNA, computer software, chemical formulae, and more. As these issues become more complex, patent law has to evolve to address new concerns. For example, one can now patent business models and software through the U.S. Patent and Trademark Office (USPTO)."
If this argument is valid, it means that APIs are not copyrightable, they are patentable, because copyright is only for expressions of ideas, not for machines; patents are what apply to machines. And Oracle has already lost on the question of patent infringement in this case (back in 2015, IIRC).