Smith, who turned 34 last month, has regularly spent time in New York City and proposed to his wife Dani there in 2017. He has previously floated the possibility of playing in MLC, telling the Sydney Morning Herald that finishing his career in the USA "would be pretty cool".
"As a New South Wales boy, the partnership the Freedom has with my home state means a lot to me," Smith said in a promotional video. "Cricket in Australia has a rich history and I look forward to being part of taking cricket to the United States of America."
Australia don't have any fixtures in their Future Tours Programme commitments during MLC's July window next year, with an away T20I series against Afghanistan at the end of August their first scheduled tour after the men's T20 World Cup in the Caribbean and the USA in June 2024.
Smith declined to comment on his long-term career plans at the start of Australia's ongoing tour of England, ahead of the World Test Championship final against India, but would be able to play in MLC while continuing to play for Australia as a centrally contracted all-format international.
"Steve has a close relationship with New South Wales and Sydney Sixers," Klinger told ESPNcricinfo. "He obviously had five fantastic games in the last BBL, and to have him on board as an ambassador to promote the team is great. He's going to really lift the profile of the Washington Freedom.
"We've got a few very strong New South Wales players who we'd certainly be interested in chatting to"
Michael Klinger
Henriques, Ben Dwarshuis, Josh Philippe and Tanveer Sangha are the NSW players due to appear for Freedom in the inaugural season of MLC, which runs from July 13 to 30. A number of Australia's most high-profile players are products of the NSW system and Klinger hopes to convince some of them to appear in MLC's second season.
"We've got a few very strong New South Wales players who we'd certainly be interested in chatting to," Klinger said. "Some of the fast bowlers often want to take breaks, especially straight after a World Cup, but in saying that, they'll be in the America and West Indies area, so hopefully they'll be keen to come and play for us.
"You've got [Mitchell] Starc, you've got [Pat] Cummins, you've got [Josh] Hazlewood. Sean Abbott is involved in that group now as well. We have some really good options next year plus our current high-profile overseas we've got this year - hopefully we can retain some of them as well.
"Especially coming off the back of the World Cup when they're already over here anyway, hopefully their schedule allows them to take seven to ten days off on holiday somewhere around this area and then they can join up and be involved next year."
Freedom are due to play their first MLC fixture on Friday night, against Seattle Orcas in Dallas.