Kerr, captain and all-time leading goalscorer for the Matildas, has missed much of the tournament due to injury but has watched on as 10th-ranked Australia have rode a wave of momentum to reach the last four for the first time.
The fact that Kerr's goals have not been needed, with forward Hayley Raso stepping up and scoring three, shows that the co-hosts are strong as a unit, Wiegman said.
"Of course, she's a threat. She's a very good player. So lots of respect. But there's more than Sam Kerr, because at the end it's always a team performance," the Dutchwoman told a press conference on Tuesday.
"And when a team does really well, an individual can do even better. That's the same for Australia, it's the same for England.
"So it's a lot of pressure on her because everyone expects things from her and for her team.
"I think Australia grew in the tournament, too. They had some disappointing situations and had to come back from them. They did really well. So we expect a very strong Australia tomorrow."
The clash at Stadium Australia will be memorable no matter what the result, as both sides aim to book their first appearance in a World Cup final.
Wiegman predicted a "tight" game but was boosted by her team having no fitness issues - possibly giving them the edge after Australia went to extra time and penalties in their quarter-final against France on Saturday.
"We have a fit group, we recovered really well again (from the win over Colombia), so we will be at our best tomorrow, physically, and so football-wise, too," she said.
England won their first major title at the Euros on home soil last year so will be wary of Australia being backed by almost 75,000 fans in the stadium, and millions watching at home, desperate for their side to achieve a similar feat.
"I don't think they're the underdog, they play at home, the stadium will be beautiful. I think there's two teams that are very good and very strong and have grown into the tournament," Wiegman said.
"So I think it's going to be very tight and it's going to be very, very competitive. And we approach the game as any other game, we prepare how we want to play, we analysed our opponents really well.
"So hopefully we can take out the strengths and exploit some weaknesses."
