Americans use it, too, in words like 'button' and 'mountain' where the /t/ becomes a glottal stop. Also in some gerunds like "putting" as in "puttin' up with". You can also sometimes hear it between words in an expression like "set in his ways" , where that /t/ too becomes glottalized.
America is a form of ethnocentricism. We prefer nowadays to use either the United States of America or the US. Canada and the US are in North America. Then you have all the countries in South America and in Central America. To use ''America'' alone means any country in all 3 Americas. It is important to show respect for the countries of the 3 Americas and not assume that all comes from the United States of America or from the US. Thank you.
Arabs say 'Imreeka', Iranians say 'Emrikaa'. Americans tend to say 'the US' or 'the States'. But keep in mind that Mexico's official name is Los Estados Unidos de Mexico, so saying the US doesn't necessarily narrow it down, either.
I understand and sympathize with your point, but I think you're fighting a losing battle. Ultimately, you can't legislate how people talk.