Monopoly is if one corporation owns an entire market. This is about multiple corporations. The proper word is cartel or "corpocracy" which dislike as corporations are just a legal fiction. Someone still owns the corporation. The article isn't really about americans not owning stuff. It is about average americans not owning stuff. Poor, or at least not-rich, people are today less likely to own things like houses and cars. But the rich still own plenty. They are owning a greater percentage of everything. So perhaps the best word is plutocracy.