I wouldn’t say it’s broken because of the FI, I watched the number 1 ranked player lose doing the FI so for lower skilled players it’s certainly beatable. It’s only really the 9 soldados +2 falc shipment that’s ridiculously good. None of the units they receive are upgraded either, they’re basic age 2 soldados and if you’ve scouted the FI then you should be in fortress, so you can train a culv and ship skirms to deal with it.
A soldado can’t beat 2 regular basic musketeers, let alone triple carded redcoats, my point was that 1 soldado does not equal 2 musketeers, 2 regular musk are stronger and will win despite them having the same population. Soldados are pop inefficient units.
Despite being inefficient, they have very few upgrades the only 1 being grenade launcher which at most gives the musketeer some late game utility, they still get shredded and kited by skirmishers and destroyed by artillery, the unit is very far from op.
Regulars might be more expensive but they have more range which matters significantly when you have a mass because the second or third line of regulars can be firing when a normal musk may not be.
Mexico do have those us style shipments, but there more of an option yes than a necessity, I’d put cuirassiers in for example if I didn’t want to use as many cav upgrades, I’d just use cav combat then rather than cav combat, caballeros and possibly the age 4 ability tech for chinacos.
I main USA and I wouldn’t say mexico are an improved version, USA is a great and very unique civ with many options. USA can also play aggressive age 2 with spanish immigrants and forward rax, standard FF with regulars and gatlings, Marine FF, California FI. All great strats.