Why do they need to have some of the best support weapons: .50cal, 57mm AT-gun, Pak Howi while at the same time having the best heal that can also be used to recinforce outside of base, 3 different types of OP T0 call-in infantry,
You're just trying to find things to complain about that really aren't issues at all. Play USF a lot and you might have different opinions about these things.
free squads when teching,
If you're paying for it, they ain't free. This mechanic has existed for years, and you're seriously crying about it being broken? USF has consistently been one of the most underpowered factions in the game, and still is to a certain degree. Right now it's in a better place because of the teching changes however.
tank crews, the straight up best TD in the entire game,
You're complaining way too much about mechamics that have existed for years. Also, the Jackson is a good tank, god forbid USF, a faction which lacks any super heavy tanks have the ability to counter Axis's high health, high armor vehicles. I'd also argue that the Jagdpanzer IV is a better TD in most situations because of its health, penetration and veterancy abilities. The Jackson is good, but it needs infantry to spot for it. Jackson used to be a glass cannon with hardly any health and massive sight, is that really where you want to return it, where it could self spot?
a excellent medium tank that wipes infantry like crazy, cheap access to grenades,
Sherman isn't even that much of a wipe machine, in my experience (thousands of hours playing usf) the Sherman is hit or miss most matches I play, it's hard to get them to vet3 where they become very effective and accurate. Most of the time you don't even want HE equipped because of the thread of other tanks that you need to be ready for at that stage of the battle.
As far as the grenades go, they are some of the worst in the game, and most people don't tech them because a) they're expensive to throw and you need munitions for weapons and b) they're easy for any competent player to dodge because of the animation being incredibly obvious and easy to spot. They're usually only useful on the first grenade if a player isn't paying attention, and then after that only useful on unaware units or garrisons.
cheap access to weapon upgrades etc.
Uh, it's not cheap, it's 150mp, 15 fuel and then you have to actually pay for the weapons themselves, which are 60mu each for BARs, 70mu each for M1919, 50mu for Zooks, and Zooks are terrible against most axis vehicles which they can barely penetrate.
Playing vs USF feels a bit stupid at the moment, especially Pathfidner doctrines with cheap weapon drops makes it seem like USF got endless amounts of units/MP.
Pathfinders are 290mp, they are very expensive as a starting unit, but I believe they should have a similar cooldown to I&R Pathfinders.
USF hasn't even seen that many changes, the most substantial was the teching changes, but all the other changes have been commanders, such as the CP reduction to the greyhound, and subsequent nerfs to I&R pathfinders and the pack howitzer. Then the changes to assault engineers in armor company as well as the addition of cavalry riflemen to mechanized.
As far as balance goes I believe USF is in a decent spot right now, my one gripe being Riflemen performance early vs. volks, but that's an issue pretty much all allied factions have.