Short answer: Grenada is the only Caribbean CBI country with a US E-2 treaty. From a USD 235,000 donation you obtain a passport that can then be used to apply for a US E-2 investor visa (typically from USD 100,000–150,000).
Two-step path
- Obtain Grenadian citizenship (donation or real estate).
- Apply for a US E-2 with the Grenadian passport and run a business in the US.
Versus Turkey
Turkey also has an E-2 treaty, but the real-estate threshold is USD 400,000. Grenada is generally lower-cost and visa-free to Schengen and the UK.
Note: some cases require prior residence in Grenada before E-2; confirm the latest rules.