The math is not universal.

The USMC 13 squad is unique and even its leaders cannot insist that nothing changed after they took some casualties.

Squads of 7-10 are usual, 9-10 seems to be typical for LI.

Percentage of force that become casualties is not generally large enough for that to be mission impactor in most cases.
Sorry, but that's the unique experience of a country that never joined really big wars early on and that never fought against intact 1st rate armies.
And even under those conditions, U.S. forces were at times very much decimated, including complete destruction of battalions (1943-1950).

I don't bother to think much about future conflicts against 3rd rate opponents because those tend not to be real threats until we turn them into foes.
Competent enemy forces can inflict serious casualties, easily up to half the infantry of a brigade turning casualties in a matter of weeks.
The Western world just avoided to fight such opponents since two generations (there's no guarantee that our governments will be able to keep it like that).