okay, I figured it out, sort of. I had to change my unit size option to normal. this caused all the recruitment options etc... to show 76 as the max size for spear militia, this is correct for the size we are playing on right.
However, I still have a number of units of 126, or 151 men left and am not sure what to do. I suppose the host could locate them all, use the console to get rid of them, and then add new units of the correct size with the console, but that is a lot of work. I am very sorry about this, and I hope it is clear this was unintentional, and I still don't understand how it happened, and why only to France. I have never needed to change unit size before, even when the hotseat was using a different one.