Final answer:
Apple's iPhone is an example of a real product and company where a firm practices market power in the US.
Step-by-step explanation:
In the U.S., an example of a real product and company where a firm practices market power is Apple's iPhone. Apple has a significant market share in the smartphone industry and limits consumer's freedom to switch to another firm by creating a closed ecosystem. This means that iPhone users can only download apps from the Apple App Store and are limited in customizing their devices compared to other smartphone brands.