Really not sure what game you're playing (or maybe you don't play because you constantly clutter the forum with overly biased and ignorant posts?)...
First of all M1919A6 (defensive stance activated) beat every single infantry squad in the game by a mile. There is no infantry counter to this and OKW lack AI vehicles. Even without defensive stance they have an amazingly strong weapon profile and put out suppression. They're, by far, the best weapon upgrade in the game. Oh and if you don't feel like going the infantry commander you can get them on Paratroopers - which are arguably the best infantry squad in the game. (6 men, self healing, M1919s, reinforce on the field, spammable suppression fire, etc etc). I'd be shocked if defensive stance and/or M1919s do not get heavily nerfed - but currently USF absolutely dominates every other faction in terms of infantry.
Yes. Facing it is a fucking joke.
M36 Jackson is an absolute beast. It stomps the Puma, Luchs, and KT while still doing great against the Panther and the Jp4. It does not fear schrecks because of its mobility. As for against Ostheer, it completely hard counters everything in T3. Still beats Panthers (which are not at all viable to field in a 1v1 as Ost) and is extremely solid against Tigers. I will admit that Jacksons have to be afraid of the Pak40, which - when combined with Tigers - probably gives Ost the advantage in the late game.
It would want to roflstomp the Puma and Luchs, it's a fucking expensive tank and they're light vehicles. I think the Puma is terribad as well, its pathing is worse than AIDS. As for everything else? I don't know what pipe you're smoking. It will get fucking wrecked by a Panther, JP4, KT or even a PzIV. It can't take a fucking hit. Schreks also fuck it. Its armour is made out of paper.
Which would be fine if the maps were designed worth a shit when it came to vehicle usage and flanking ability. The only maps in the game that are close to that are the ported CoH1 maps.
M8A1 is also really good, I prefer the Sherman but plenty of top players combine the M8 with Jacksons and other AT to great effect.
The M8A1 is a mid game light vehicle, which is sad because it's better than the fucking Sherman. Earlier shock value, can handle light vehicles, rapes infantry, a well microed M8 is the flat out superior choice to a HE Sherman.
As I've mentioned earlier in the post USF has the best forward retreat mechanic in the form of the Major + Ambulance, and has a huge advantage over everyone in terms of repair speed. RET repair faster than all other engineers except for Sturms with the minesweeper package, and when combined with tank crews the USF can repair their tanks almost instantly.
The forward retreat is not something to brag about. The Major is weak as fuck and he's Tier 4. OKW get that the first thing in the game. For being nearly three times more expensive with 1/10 the durability, I think having a mobile base of Med Truck + Major is quite alright. It's something I will use almost every game, but it's the most expensive forward base option and by FAR the most vulnerable(Excluding USF Infantry Co. arty strike BS). Doesn't help that Med Truck has the worst profile and worst pathing in the game for what it is.
Right now Ost and USF are definitely the top two factions. I give the slight edge to Ost because a late game of 3-4 Grens, 2 MG42, 2 PAK and Tigers is probably unbeatable. USF *can* win against Ostheer thanks to their early game prowess and they're significantly stronger than OKW and Soviet.
In 1v1 I definitely feel like USF is the top faction. That doesn't come from their late game strength, it comes from their overwhelmingly strong early and mid game, which compensates for how shit their late game units are.