[pseudalopex]

Words can mean different things in different languages and different contexts.

In English-speaking cultures, North and South America are separate continents. "America" is understood to mean the USA. The polite term for someone from the USA is "American". Calling a Canadian "American" is impolite.

In Spanish-speaking cultures, América is a single continent. "Estados Unidos" is understood to mean "de América", not "Mexicanos". People from the USA are commonly called "estadounidense", "norteamericano", or "americano". It's polite for outsiders to use "estadounidense".

Neither language is indigenous to the Americas, so why not just use the polite words in each language?