Hello! Watched your replay, here are some tips:
General problems
Basic stuff
Never fight 1v3 battles. Not even from garrisons. If you stay, your troops will suffer a big health drop and probably will die on retreat. There are a lot of anti-garrison tools too if you decide to stay. Try to pick fair fights or unfair ones (to your advantage).
Grenade tech totally unnecessary that early. It delayed your first Stuart from hitting the field, the right time (12 min stuart) therefore giving the enemy great advantage. Overall: Grenade tech (cost + throwing them) didn't pay off.
Use prioritise vehicle on ATGs, TDs and assault guns. Your ATG was shooting at infantry 90% of the time. You could've killed the Luchs if the ATG wouldn't have fired at infantry right before Luchs disappeared.
Micro
Focus down low health / weaker squads or the ones that means the biggest threat for your troops. There were a lot of moments when you could've wiped a retreating squad. On the other side your troops fired at volksgrens in heavy cover, long range, where his Sturmpio closed in unharmed.
Use attack move "A-move" every time, so units won't literally run into enemy units just to get wiped + they'll have better damage output (since they are standing, there's a big penalty to accuracy while on the move).
Queueing up orders with the SHIFT button is a must if you want to improve. This way you can send a single soldier to cap points in a spectacular order or for example: send unit to point with A-move, shift click cap the point and shift A-move to another point etc etc.
Use control groups. You can assign a unit / units to a group by pressing ctrl + "number 1-9" when the squad is selected. Don't use more than 1 (max 2) squads in one group. So when you see your unit engaged (the little flashing icon on the upper right corner under the squad) simply double press the corresponding button, and you can decide within seconds whether to leave them to fight or retreat.
Know the units
Pay extra attention to units in houses vs OKW as they have flame nades, they always got you, chopping off 10-20% health.
Immedietaly retreat if sturmpio reaches close range. If they don't lose a model or 2 they'll win the every fight in close range (except: upgraded infantry / thompson rangers).
If you have nothing else, treat a Luchs with an AT nade and retreat, lone rifles won't win against it.
If you want to succeed in the mid-game where light vehicles roll out, you need to know which units can halt your tracked beasts. For example, you always dived falls that fausted your stuart. It'll come as you play more and more, but knowing what units you can dive or not can save them.
Map control / Knowing the maps
Don't be scared to increase your number of territories and map presence if you can do it without any danger. As the guy only focused on 1 point, you could've easily capped almost every point on the map.
Set up ambushes for overextending units. Secondly: Always reposition your team weapons. They come in handy for halting an enemy advance. But be sure you can give them the proper support as team weapons alone will die.
Lock down the entrances on Semoskiy (with units on one side and tank traps + barb wire on the other) if you can. Note: This only applies to summer version.
Advanced USF tips
Disembark from vehicles at base if you don't use them (less popcap = increased manpower rate).
How to play your faction (AKA faction "mindset")
Be a lot more aggressive. USF has some of the best stock infantry that can deal with everything given the right conditions. As USF doesn't rely heavily on team weapons like other factions do, their units must be on the move most of the time.
Should've chosen Armor company instead of Airborne. Assault Engies could've planted a few mines to surprise the enemy + 2 M10s can circle the KT to death without support (and he didn't have any).
Time marked problems
4.10 min mark: Second rifle standing idle behind bush, while the one next to it got raped by kübel + sturm combo.
4.40 min mark: Missed wipe opportunity. always move squads out of houses for maximum damage potential (small house with 0 windows in this particular scenario, knowing the maps houses and stuff will help this).
5.10 min mark: Idle rifle in church, could've capped VP and standard point.
12.45 min mark: Stuart got fausted (see the "Know the units" section).
13.05 min mark: 2 rifles standing idle at base. That's alone a big issue, no explanation needed I think (if there are squads at base for more than 5 seconds after they are ready to go (fully healed, reinforced) you are doing something wrong.
15.45 min mark: Riflemen and captain capping a point. 1 squad is more than enough to cap a point. should've capped VP with rifle.
17.40 min mark: Could've destroyed the SWS truck with your stuart. I'm still dying inside why you didn't do that. It would've been such a heartwarming moment + no armor for OKW guy.
19 min mark: Second stuart was a total waste. Should've teched to major. You saw the sws truck, out in the nowhere, of course it's gonna be a T4. And yes, you teched major after it. It must've been INSTEAD of it. Only buy 2 light vehicles if you are in resource income advantage and lost your first one.
Final conclusion:
You played so-so, but you must be super aggressive with USF compared to this match, vastly improve unit preservation and watch out for enemy movements.
Hope I helped!
Cheers