The 24-year-old winger joined the Warriors in February and was part of the Glasgow squad which won the Melrose 7s in April.
Born in Ohio, Isles scored 27 tries in 14 sevens tournaments for the USA national team in the IRB Sevens World Series and also featured for his country at the Rugby World Cup Sevens in Russia last year.
He came to Scotland to learn and develop as a winger in the fifteen-a-side game, but with Rugby 7s set to debut at the 2016 Olympics in Rio he has decided to concentrate on trying to get into the USA 7s squad.
Glasgow Warriors head coach Gregor Townsend said: "Carlin has come in and trained really well with us, but he has decided he would like to concentrate on 7s and we respect that.
"It's an exciting time for the sport, with it set to debut at the Olympics in 2016.
"We'd like to thank Carlin for coming over and we wish him all the best for the future."
Carlin Isles said: "I'd like to thank Glasgow Warriors for giving me the opportunity to train with them over the last few months.
"I've learnt so much from the experience and made some really good friends.
"However, I want to focus on 7s and if I work hard hopefully I can be part of the USA 7s squad at the Summer Olympics in 2016."
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