Thing is, the allies actually can't put 3x more bullets into the air.

By technicaly adding up the rate of fire you get abou 20 RPM for each Garand 30 RPM for the carbine 600 m1919 300-400 BAR

Let's just round it up to 1500 rounds per minute for the whole US squad.

And for the German squad we have: 5-10 for a Kar98k 20 for a G43 1200 for Mg42 450-600 STG 44 500 MP40

I mean even if you just had an AR and the MG alone you would manage to put more bullets down range than an entire allied squad. These numbers don't take reload time in account and are probably not super accurate but they still serve as an example.

Granted the German firepower relies heavily on one person fielding a big portion of that firepower though still its also possible to form squads of up to 5 man without jmhaving a Kar98k at all.