English is spoken around the world because of the British Empire and its colonialism. Also because the US is currently the most powerful economy in the world. It is true that English is a popular language around the world because of business and tourism. However, it IS NOT TRUE that English is not taught here in this country, and especially not true it is taught with less vigor or competancy than it is in other countries. That's just a silly myth. I know. I was an international teacher for many years as well as having taught in the US for many years. The problem with US education is not the curriculum or the teachers. The problem is a public that, like you, excoriate our teachers, schools and education system at every turn. The problem is parents who teach students to have little or no respect for teachers or for their schools. That don't take any interest in their children's education. At every single parent teacher event that I experienced when I taught in the US, only a tiny minority of parents attended to talk to the teacher and understand their child's progress, and those parents were mostly parents of students who were doing well.
It is the culture, the attitude toward education and teachers in this country that is the problem. I taught overseas side by side with teachers from all over the world, including American teachers, and there was no difference whatsoever in their level of competancy. None. It isn't the teachers and it isn't the curriculum.
And by the way, it isn't 'American English' that is being taught around the world. International teachers generally teach British English because most of those teaching English outside this country are either British or were taught themselves by British teachers.