America is the widely used casual name for the United States of America. Context matters.

https://en.wikipedia.org/wiki/America

"America usually refers to either:

"The Americas, a landmass comprising North America and South America

"The United States of America, a country in North America"

This actually is reasonable since US is the only country with `america' in its name. Other countries have fancier names that can be used to easily recognize them.