Mueller struck twice in Bayern's 4-0 victory against Barcelona last Tuesday, a day before Robert Lewandowski netted all four of Borussia Dortmund's goals in their 4-1 humbling of Real Madrid.
Dortmund will seek to protect their advantage and secure a place in next month's final later on Tuesday at Real's Bernabeu stadium, before Bayern, last season's losing finalists, run out at the Nou Camp on Wednesday.
"They were two extraordinary results," Mueller said.
"Both those first legs were in Germany and I think the two Spanish teams will be stronger in their own stadiums," added the 23-year-old Germany international.
"Essentially though it suggests that what has been said the past few years was not rubbish, that German football is on the up," he said. "It's fun to be part of that and you can see it in the national team as well.
"But it's merely a good sign, nothing more and nothing less. Let's wait and see who gets through to the final."
Bayern were the last German team to win the Champions League back in 2001 and were also the last Bundesliga side to win the UEFA Cup/Europa League in 1996.
Spanish teams have won four Champions League crowns since 2001, with Barca triumphing three times, and five UEFA Cup/Europa League titles since 1996.
World and European champions Spain have dominated the international game in recent years, beating Germany in the final of Euro 2008 and knocking them out of the 2010 World Cup in the semi-finals.
Bayern coach Jupp Heynckes, who has experience coaching in Spain at Barca's great rivals Real, Athletic Bilbao and Tenerife, should have a full squad available for Wednesday's game, with only defender Dante, who has a cold, a doubt.
A striker himself in his playing days for Borussia Moenchengladbach and Hanover 96, Heynckes said Bayern would not be curbing their attacking instincts.
"We are not a team that just defends," the 67-year-old, who was born the day after World War Two ended in Europe, said.
"We are very good defensively, we know that from the Bundesliga and also from European competition," he added.
"But we are also a team that can be creative going forward and we want to try that tomorrow."
Heynckes also said he will not be instructing his team to play a cautious game on Wednesday despite six players, including defender Philipp Lahm and midfielders Bastian Schweinsteiger and Javi Martinez, risking suspension for the final.
"Our approach to the match will be the same as always," Schweinsteiger said.
"We'll be going into the tackles the same way we usually do and if it (suspension) happens then it happens.
"We have opened the door to reaching the final but we have not yet taken any steps through it."
The final is at London's Wembley stadium, where four-times champions Barca won European titles in 1992 and 2011, on May 25.