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Cressy will play his third championship match of the year on Monday (AEST) after a 6-2 4-6 6-3 defeat of his fellow American in Newport.
The 25-year-old fired down 22 aces and won 82 per cent of points behind his first serve, breaking three times to move into the final.
Cressy had a stroke of luck for the only break of the deciding set, when he lobbed a shot just over the net and it bounced back onto his side to leave Isner 5-3 down. He then served out the match to end Isner's 10-match winning run in this event.
Bublik sealed his place in the final with a 6-3 6-2 victory over Australia's Kubler.
No.3 seed Bublik did not face a break point and broke the Australian three times, sealing his victory in an hour and nine minutes.
There will be an all-Argentinian final at the Swedish Open between Francisco Cerundolo and Sebastian Baez.
Baez produced an upset, securing his first win against a top-10 opponent with a 6-2 6-4 defeat of No.2 seed Andrey Rublev in Bastad.
Cerundolo got the better of Pablo Carreno Busta 6-3 6-2, ensuring he will face his compatriot for the first time at tour-level.