A typhoon set to hit the Suzuka circuit on Sunday forced the cancellation of both races, leaving Gasly half a point behind new champion Hiroaki Ishiura.
Gasly's absence from Austin has paved the way for New Zealander Brendon Hartley to replace him at Toro Rosso and make his Formula One debut in Sunday's race at the Texas track.
The Frenchman is expected to return to Formula One for the remaining three rounds after Austin and to take on a regular race drive in 2018.
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Hartley acquitted himself well in Friday practise, completing more than a race distance, and could also be in the frame for a race drive next year if Toro Rosso decide to drop Russian Daniil Kvyat.
The driver turmoil at the Red Bull-owned team is a consequence of Kvyat's poor performances this season and Spaniard Carlos Sainz's move to Renault as part of an engine deal that will see Toro Rosso switch to Honda in 2018.
Gasly was racing in Japan for a Honda-backed team before making his Formula One debut in Malaysia this month.
(Reporting by Alan Baldwin, editing by Ed Osmond)
