I know that this is popular especially among Latin American speakers, but the phrase "US-American" is very unidiomatic in English and makes you stand out quite significantly. In English, the term "American" means someone from the United States of America. It's clear enough because "America" is always a shortened form of that country, while the large western hemisphere landmass is collectively "the Americas", since the anglosphere almost universally uses a seven-continent model with North and South America being two continents (and with some more "enlightened" people preferring a six-continent model merging Eurasia—but you'll rarely find a native English speaker who refers to "America" as a single continent).