I am not nor ever have been in any armed force, so take or leave my comments, they are just my opinions. They are neutral with to regard to the USA vs USMC food fight. I might as well chime in her about some subsequent posts.
Modern USMC: I would rate as 9-5-Y because of the modern usage of 5.56 mm vs WW2 7.62 mm 30-06, less round carry overall vs 3 GPMG giving better volume at distance. However the distribution of Grenade Launchers means I would be inclined to add an extra FP for a 10-5-Y. (I am staying out of the 7 vs 8 morale question, life is too short). I mentioned in my post, that I pointed to earlier, that the standard 4XY squad varied from 7 to 12 (with the Poles having a 20 man squad) and still only rated 4 FP as the number of bolt action rifles really did not make much difference to the FP. In the same post I said that in a SMG or mainly SMG squad, the number of troops does matter, so the size of the squad does matter with a modern Assault Rifle + GPMG squad. The yardstick is the Soviet 628 which historically was 10 men with SMG and no LMG. So my guess for a modern 8-9 man APC squad with AR, 2 LMG and GL would get something like 3/4 for 6 AR, 2 for 2 LMG and 1 for (some) GL to total from 6-4-Y to 7-5-Y, depending upon the designers taste. The usually larger leg or truck mounted squad does get extra due to its greater size unlike WW2 rifle based squads.
USMC squad breakdown: The various 5 FP squads break down into 2 FP HS, the USA paratrooper 747 and German 838 both break down into 3 FP HS. It simplifies the 'book keeping' and I suppose the justification is that those squads loose any extra edge when divided. So the current 768 -> 2 x 348 seems OK to me. I would have been happy with the alternative 3 x 248, though that would cause problems with the normal K and 2nd squad morale fail, never mind if you mix 458 in with your 768 to represent rear area or technical troops. Seems like far too much (rules) trouble to breakdown into anything other than 2 equal HS, compared to the gain. ASL is complicated enough.
USA squad: On the surface a 556/557 would seem more accurate, but from what I have read, many USA squads added a 2nd BAR unofficially once they had been in combat a little or alternatively or in addition a few SMG. So 6 FP is not unreasonable. From my little bit of rifle firing, not having to move your trigger hand to work a bolt meant that I could keep better on target (rabbit). So overall I will not begrudge the USA E/1 squad their 666/667. I have, on the other hand, in the past said that USA squads 'fresh off the boat' should be represented by 2nd line 546. That better represents the official TO&E and their lack of experience and cohesion.
There are a couple of squads that I disagree with, the German 838 and USA 747, as neither correspond to any real TO&E, that I have seen anyway. Both are in effect SL era bogeymen. The US '44 paratroop squad had 2 M1919A6 LMG (later a BAR replaced 1 M1919A6) so a 6 hex range would be justified, indeed a 6-6-7 would be closer. German assault engineer were, with the exception of FT and DC (both separate SW), fairly identically armed to the infantry. Throw in an extra FP for mini-DC and other general nasty tricks to give them 5 FP (or higher for late war). Thus a 548 or 648 would be a lot more accurate for the vast majority of German AE.