Kann irgendwie aus dem H-2B-Visum eine GreenCard werden (USA)?

Ja, das geht. Der AG muss als Sponsor fungieren:

To move from your H-1B Visa onto a Green Card you’ll need your employer to sponsor you. You’ll be applying for a Green Card on the basis of your employment¹, and will need to check you fit the full eligibility criteria for the work based Green Card, over on the USCIS website.

Quelle