>So I would refrase it to "Some ESL speak better English then OTHER ESLs" and "Some Americans speak English badly by their own choice"
As an ESL myself, I agree.
But to address what ToniL said, the reason many ESL speak or write better English is:
1. They had no other English choices.
2. Not all ESL are good in it really, but, in your (our) profession, one will tend to run into "overachiever" ESLs. ESLs who don't exert extra effort at what they do are usually not even here (US). Those you meet here are usually special in their own way.
Imagine, getting up one morning and deciding that you were going to buy a ticket, and leave everything you ever knew, in order to start a new life in an alien nation. That's special.
That's also why this country (US) is so special to many of us: we are mostly foreign people who came here to really work hard and change things. Immigrants built this nation.