Mbappe, who recently signed for Real Madrid, said Sunday the snap parliamentary elections set for June and July came at a "crucial moment" in France's history.
Mbappe was defending comments made by compatriot Marcus Thuram, saying the Inter Milan forward "had not gone too far" in calling on the country "to fight every day to stop" the far-right National Rally (RN) winning the elections.
However when asked about Mbappe's remarks, Spain's first choice goalkeeper Simon said players gave their opinions too much on topics like politics.
"Kylian is someone who has a lot of influence in the world, in society," Simon told a press conference.
"In the end it's a political topic. I think we sometimes have the tendency to give opinions too much on certain topics when I don't know if we should or not, I don't know if we should do these things.
"I'm here, a football player, I focus on football, the only thing I should be talking about here with you is sporting topics, and leave politics to other people and organisations."
After Thuram spoke on Saturday, the French Football Federation issued a statement demanding the team not be subject "to any form of pressure and political use".
The FFF said that although they respected freedom of expression they "wish (their) neutrality to be respected by all... as well as that of the squad".
However, Mbappe, 25, on Sunday backed Thuram and his remarks.
"The Euros is very important in our careers, but we are citizens first and foremost and I don't think we can be disconnected from the world around us," said Mbappe.
"Today we can all see that extremists are very close to winning power and we have the opportunity to choose the future of our country.
"That is why I call on all young people to go out and vote, to really be aware of the importance of the situation.
"The country needs to identify with the values of diversity and tolerance. That is undeniable. I really hope we make the right decision."
Tournament favourites France face Austria later Monday in their Euro 2024 opener.
