USA is actually my most played civ, as after release I played a ton of just USA.
Having seen and tried all of it’s strategies here are a few good and bad points.
Low and slow eco, traditional builds with usa just are too slow and when you check all resources gathered you will be significantly out gathered by almost any civ until the 25 min mark, from my experience there’s only 2 ways to match eco, either send french and irish immigrants 1st to copy the traditional 3v,4v shipments of other civs or use chinese immigrants to control a tp line with stagecoach.
Terrible anti-cav, carbine cavalry are 1 of the least used units quite simply they are bad dragoons, in most match ups this cav weakness is over exaggerated at least in 1v1 where there’s just not that much cav in general, and with arsenal you can get the socket bayonet tech which improves your regulars in melee vs cav(+20% attack in melee) as well as the hp tech which is more then enough in most games as regulars are great musketeers.
1 of the strongest turtle civs, with usa and the capitol building you can quickly build tc’s and outposts without having to use villagers or your explorer, making it very difficult to push your base without mortars. General can also build and rebuild forts, can place the flag mid map to increase the speed units train and buff them near the flag to make a strong forward base.
There are several cards to get mill wagons which you will need if doing a 3tc boom and turtling because you will quickly run out of food, however with limited deck space i feel it’s better to get max woodcutting upgrades with hamiltonian economics and that will aid in building mills when needed and production of gatlings/state militia and of course outpost spam.
USA also have access to a ton of trickles which helps when turtling, you can get the bank wagon, capitalism trickle, xp trickle from spanish immigrants, age with pensylvania and get the church gold trickle worth another bank as well as pensylvania gives you church wagon and increases build limit so you can now get 2 churches trickling xp. Factory in age 3 as well, you can really get a strong eco with all these things combined, although it is very greedy and may not work well against any aggression.
4.State militia are probably the best standard unit in the game, unfortunately they need the long rifles card or their range is bad but with that and springfield armory techs: counter infantry rifling, flint lock, paper cartridge and military drummers which all research fairly quickly and for free they become a powerhouse in age 2 and beyond. That will give them extra multiplier vs heavy infantry, +10% hp, +15% attack, +10% speed and state militia gain more hp up to 30 units so they become very fast, beefy, cost-effective skirms and with high hp can even stand up to cavalry. Also have an upgrade card in age 3 to make them even stronger, there’s an age 4 federal card that gives them an additional +10% buff from the flag.
Unfortunately even with all that USA still isn’t the best turtle civ, portugal are by far the best on water and on land inca have usa beat quite significantly with their strongholds to garrison units, 2 building hp cards, stealth fort/warhuts, houses producing food, strong archers, chimu runners to raid. usa just falls short but it is still a fun civ to use and can be viable just know that you will be at a small disadvantage vs most civs.