Americans (inhabitants/citizens of US) when people from other countries come to theirs : "These people need to speak English"
Americans when they visit other people's countries : "Why don't these people speak English???"
EDIT : By the context of this post it's blatantly obvious which definition of 'American' is being used lol, but I added an explanation above anyway. ๐ And yes there is more than one definition of "american", usually context makes it clear which is being used for most people
Because that's what people from the United States call themselves.... If they viewed Mexicans as Americans there would be no problem at the border, only on dumb internet forums full of self righteous nerds are everybody in the Americas called Americans