Because yeah of course, losing a model in a squad of 4 men isn't as big of a deal as losing a model in a squad of 5 or 6. Captain Nonsense ? When you lose 1 guy in a gren squad, you lose 25% dps, then 33%, then you retreat because you can't afford to lose the squad or it is gg. While having 5 men squads allows your squads to fight longer (obvious i know), have more dps in the long run (even if both squads do the same damage when they are full health/models), and is far less punishing for a mistake. That's exactly like Gbpirate explains: where allies are more micro intensive in the late stage of the game (because more squads and generally more units to handle), WM is terrible in the early. One unchecked mine, one grenade, one lucky squad wipe on the retreat can spell doom for the whole game. I already battled in another thread on this exact matter, and even uploaded couple replays of a US player losing 3-4 squads at the 15th min mark, and still fighting tooth and nail until the 45th mark, where WM finally won (and these were not casual players' 1v1s). I have yet to witness a WM player losing even 2 squads at the 15th mark, being able to fight toe to toe versus USF until 40 minutes into the game, let alone 4 squads. But as usual, i'm being told that i know shit, and holy grail holder noobitof pushes his allies agenda for another 500 posts.
It all depends on how you are trading and engaging. Grenadiers are weak in the early game, which is why you either need to outnumber him or use support weapons like MG42 and Sniper to win the engagement. Once they get the LMG, losing that one man isn't 25% of their DPS anymore. The single LMG grenadier alone does more damage than the other three models combined at effective ranges. This makes Wehrmacht surprisingly immune to snipers as a force multiplier since they're not taking away much damage by targeting your grenadiers or support weapons, they're just pressuring you. An example of what I'm talking about is A riflemen squad at 3 men will lose to a Pio squad for example, due to the loss of DPS. Manpower bleed is still manpower bleed, but a sniper doesn't "turn the tide" of fights against Grenadiers once they get those LMG's.
Smaller squad sizes have their advantages and their disadvantages. They're better in cover, especially against MG's, better in buildings and generally don't spend as much on reinforcement since they retreat earlier. The disadvantages is that an unlucky mine or mortar hit can be really bad for you. They also work really well with in field reinforcement like Halftrack or reinforcement bunker, because you can actively gain a huge percent of your damage back when you reinforce and is a wholly underused aspect of Wehrmacht quite frankly.
Chances are if a US player gets tons of squad wipes and can still compete it's because the german player isn't pushing their advantage hard enough. Lots of players in this game are really passive. This is why Allies typically win if German loses a few squads: they are very aggressive with their infantry and light vehicles and they punish you harder for those early game mistakes. A great follow up to early game squad wipes is to bolster your support weapons with things like mortars or more machine guns which limit his options of moving around the map even further. (While mining up of course)