Danny Welbeck's second-half strike on his first return to Old Trafford earned Arsenal a 2-1 win over United, who saw Angel Di Maria sent off late on for a tug on the shirt of referee Michael Oliver having been booked.
The win kept alive Arsenal's hopes of retaining the FA Cup and Wenger's men will now face the winner of the replay between Reading and Bradford City in the last four.
But Wenger, whose side required extra time to see off Wigan Athletic in last year's semis, does not expect an easy ride.
"Last year we played a tricky game at Wembley in the semi-final and we expect that again," he is quoted as saying by BBC Sport. "I thought we played well [at United] and deserved to win the game.
"We had to start without apprehension and play at a high pace and we did that well.
"Danny Welbeck, I believe, is just happy to score. He worked extremely hard and deserved his goal."
Arsenal trail Monaco 3-1 in the last 16 of the UEFA Champions League ahead of the away leg later this month, but Wenger is confident a first win at United since 2006 could inspire his players to a remarkable comeback.
"We live in the real world and want to compete in every competition," he added. "This result can give us good morale for the Premier League and the game in Monaco."
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