Avoid the use of "America" as a substitute for "United States."
Specificity strengthens your writing. In this case, it also conveys understanding and might signal a modicum of humility.
Here is my personal story with learning the difference. Early during a study abroad experience in Oviedo, Spain, I reflexively answered the question, "De dónde eres? (Where are you from?) with, "Soy Americano." I was quickly teased and asked if I was Canadian, Argentinian.. they claimed they couldn't place my accent in "America." After a brief lecture on meaning of “America,” I learned the term "Estadounidense." It sounds like "United Statesian" in my mind and has provided me an excellent reminder to use “United States.”