Why do the US have a squad size of 10 men? what's the reasoning behind 10? The British Army uses a section size of 8. This is so it can be split easily two teams of 4, four teams of 2. Wasn't always this way, I think it was the early to mid 80's that the British army changed to 8 man sections so i've only ever know their understanding of things, which makes sense to me. Everything in 2's. How do the US break their squads down in to smaller groups? is it an even split or lopsided so in favour of a larger infantry group and a smaller support weapons group?
I've been out for decades so I'm sure some details have changed, but a squad is a subset of a platoon, which in turn is a subset of a company. A squad is comprised of two combat teams of 4 men each, with a sergeant over both. So it's nine men, not ten. This may help: https://www.battleorder.org/usa-rifleco-ibct-2020
Unit size is dictated by MTOE. Mission Table of Organization and Equipment. These are set by the Pentagon according to what some overpaid civilian thinks your unit needs to accomplish your mission. Sometimes they guess right, sometimes they guess wrong. But back to the topic, I have been in squads as high as 12 and as low as 4. Sometimes, due to personnel shortages (especially if a bunch of Non-Commissioned Officers move stations) squads might get merged and you have essentially two partial squads merged into one with the remaining NCOs taking over the oversized squad.