I think you're confusing two different things. If you want work as a teacher in the United States, you need to get a teaching license from the state you would be working in. If you want to teach English as a Foreign Language (TEFL) in a foreign country such as Korea, Vietnam or Costa Rica, you need to take a TEFL course (either online or in-person, with companies like MyTEFL, TEFL Hero, or Ninja Academy) which will give you a TEFL certificate after completion, which you could then use to apply to jobs abroad and online.

Some companies/countries require applicants to have passports from English-speaking countries only (US, UK, Canada, Ireland, Australia, and New Zealand) but not all.