So what? This isn't the turn of the 15th century. Do you still wear a codpiece? Of people with a 1st-grade education or better, 99% of them understand "America" to be the United States of America. If you don't, then the reason is either:
a) ignorance
b)some misguided political assertion that the United States isn't allowed to "usurp" the title of "America" and is "arrogant" because of this.