Not all countries qualify for the E-2 visa. This visa is exclusively available to individuals who are citizens of a treaty country. A treaty country refers to one that has an established treaty of commerce or navigation with the United States. Currently, there are over 60 such countries.
To check if your country is on the list, visit the Department of State's website where you will find a comprehensive list of eligible countries. This is a crucial preliminary step toward qualifying for the E-2 visa.
Your eligibility is determined by the country of the passport you hold. Thus, your passport's nationality becomes your country of nationality for E-2 visa purposes.