The Czech team of Karolina Muchova and Jakub Mensik won the US Open mixed doubles Wednesday, saving two match points in a nervy semi-final and then pulling through in a tight final.Another Mensik ace saved one of two match points earlier in the evening when the Czech pair edged the Russians Mirra Andreeva and Andrey Rublev, 5-4, 3-5, 11-9.