The 23-year-old made 12 appearances for the Dons since joining them last summer after his release by Southampton.
The United States Under-23 man failed to keep a clean sheet as the Dons were relegated from the Championship.
News of his release comes the day after young keeper Charlie Burns was given a new contact at Stadium:MK.
Defenders Matthew Upson, Antony Kay and Jordan Spence were released by the Dons earlier in the month.
Goalkeeper Cody Cropper will leave MK Dons at the end of his deal in June after the club decided against exercising the option in his contract.