He said: "I wanted to test myself in Europe to see what I can do.
"I want to be the best player I can be, the best American player.
"Why not challenge myself at one of the biggest clubs in the world?"
Miazga is yet to play for Chelsea but has been on the bench three times including the Champions League last 16 first-leg at Paris St-Germain.
He told ESPN: "I was happy to be on the roster, or squad - they say squad over there - for such a big game after I had just got to the club.
"Now I'm hoping to make the roster more consistently.
"I know I can do it. I'm in a great situation."