The 28-year old New York native returned to his home city in February after spending 2014 with the Carolina RailHawks in the NASL.
Grella had previously spent time with the likes of Leeds United, Carlisle United, Swindon Town, Brentford, Bury, Scunthorpe United and Viborg and admitted there was a possibility to return to Europe but opted to make the Red Bull Arena his new home.
Of his choice, Grella told MLSsoccer.com: "I had options to go back to Europe, but I wanted to settle here.
"It was not as easy as I thought. I had to train a lot on my own, and sort of look into the dark and seeing what steps were next. It was a very difficult time for my wife and I because she was pregnant at the time. But I'm a big believer and I have a lot of faith.
"I'm settled back in New York with my wife and my son and I'm just so happy."
Grella has enjoyed an impressive beginning to life with the Red Bulls, having scored two goals and provided one assist in 10 appearances for the Eastern Conference's third-placed side.