Final answer:
The top-ranked American golfer in 2015 with 5 wins in 27 appearances was Jordan Spieth.
Step-by-step explanation:
The American golfer who was 2015's top-ranked with 5 wins in 27 appearances is A) Jordan Spieth. While Tiger Woods is indeed a celebrated golfer with a diverse heritage as mentioned, including Chinese, Thai, African American, Native American, and Dutch backgrounds, he was not the top-ranked golfer in 2015. The information provided about Tiger Woods' heritage exemplifies the growing diversity among individuals with multiple ethnic backgrounds.