How to Deal with Airdrop Spam
When facing paradropped Air MG spam, I think the most important thing to keep in mind is that the opponent is commiting their resources into not very mobile units. They might be able to lock down a zone, but if you change the direction of your attack and help one of your allies, they will be forced to reposition and be left vulnerable in the process. And if they don’t move, all the progress you make with a teammate can allow you to hit the flanks of that entrenched player.
If you want to directly counter the MGs, there are some tools the game gives you as the Wehrmacht and DAK. Wehrmacht has the mortar, which is a very nice counter and can become extremely useful with its vet 1 flare ability (quickly accessible with the infanterie officer headquarters upgrade). Then, you have flamethrower pioneers. These are extremely good against MGs garrisoned in buildings. The Wehrmacht’s pioneers are only 3 models, but they can serve pretty well as flanking units. I’ll also mention that the early game tool for the DAK against MGs is their mobility through the 250 halftrack, which you can garrisons units inside (most notably a panzerpioneer upgraded with a flamethrower) and catch your opponents off-guard with quick maneuvers. Remember that the USF MG paradrops are easily telegraphed as soon as you hear enemy planes in the start of the match. This lets you know right away what to expect.
As for paratroopers, they are an elite unit with very good stats. The MG42 is a clear counter, since it deals with infantry quite well. There is nothing much I can say about them other than suggesting to keep an eye on what upgrades they’re being equipped with, so you know what kind of army composition will work against them.