It's a text based game from early 2000s, but liberal crime squad is one of my favs and made by bay12games (dwarf fortress). It's operating on several layers of irony but you get to take on cops, soldiers, middle managers, CEOs and kidnap justices and even visit the president. On the highest difficulty you start is a nearly fully fascist America and need to prevent conservative laws being passed via adventurism. Naturally you win when the people the conservatism away

http://lcs.wikidot.com/start

It's been updated by some passionate fans here http://www.bay12forums.com/smf/index.php?PHPSESSID=ec71cafae4a2fde243c3562d9bcb9637&topic=159540.0

And free!

Wolfenstein let's you literally kill American nazis, and Klan idiots.

GTA V, just get the 5 stars, go to military base and enjoy!

Red Dead Redemption 2. You fight alongside a tribe under reservation against the US army after liberating an island from colonial rule.

Payday 2. Do all of the heists that don't have a "break stealth and instafail" stipulation as loud as possible, with either Razormind or I Will Give You My All 2017 as the heist BGM, and mulch as many pigs as you can. Yeah, they're cops rather than full-on military; but they DO pull up with enough special units to make one question if the police and the military in PD2 are just fused together.

Spec ops: The Line, though you do also kill civilians sadly, but you kill a bunch of Operators (TM).
Sniper Elite 4 has a skin where you can be an italian partisan woman. Then it's just slo-mo shots of nazi skulls being crushed.
Empire: Total War has the american revolution, which you can handliy crush.
Battlefield 1942 has a nazi campaign, though uhhh, you'd be playing as the nazis so.
Prototype was a sort of spider-man like game, but you could just go murder the army.
The new Wolfenstein games take place in the US.
Modern Warfare 2 has you killing loads of americans.
Red Orchestra 2 is about killing americans I believe.
If you're into strategy games then Command and Conquer.

you can play...

hitman blood money: -you literally have to kill a boer neonazi

hitman: world of assasination 1-3

-kill rich people in an island filled with rich people

-kill a banker

-kill an argentinian far-right politician

-you can kill an oil baron -etc...

Wolfenstein: The New Colossus and Fursan al-Aqsa. There's also Soldier of Fortune: Platinum Edition, while you do play as a PMC chud, you do get to fill up the morgues of NYC with neo-Nazis in two chapters with two Boers as the main villains. Also from the word go, you do at least get to remove a Nazi's face with a SPAS-12 at point-blank.

And sometimes even Minecraft when some kid builds a definetely not a swastika next to the Ukrainian flag in their base, so you spawncamp them and steal all their diamonds.

Spec Ops: The Line is probably the first example that comes to mind.

They get a bad rap because of the sometimes fascist leaning fanbase, but paradox grand strategy games do let you play whatever side you want. Everytime I tried Hearts of Iron (admittedly my least favourite paradox game), I played as the USSR.

Some of the Metal Gear games, though that's still "the good americans vs the corrupt government" which isn't really ideal either.
Yakuza 3 features CIA as one of the villain factions.

Sid Meier's Civilization (I prefer civ4)

In Metal Gear Solid 5 ground zeros, you break into Guantanamo. But it’s a very short campaign.

Pretty sure this is the entire idea of the new wolfenstein games

Victoria 3.

It doesn't really focus on killing enemies, but you can build communism somewhere in the world and squash the imperial ambitions of the US while also pushing the empires into decline.

Play as Britain, stop the US from expanding West while slowly guiding the UK towards a proletarian revolution.

Metal gear rising is about pulling cops limb from limb for like half the game, but its more interPMC war rather than real liberation

rising storm 2 lets you play in multiplayer matches as the people's army of vietnam/national liberation front fighting against american imperialist invaders. you can use traps on them, blow their helicopters out of the sky, etc.

Can't believe spec ops the line was suggested just once

This was also developed by a single comrade. https://store.steampowered.com/app/1714420/Fursan_alAqsa_The_Knights_of_the_AlAqsa_Mosque/

i heard some time ago that there was a game where you play as an vietnamese solider against usian invasion, idk if it was released of not.

there is enlisted, a ww2 online game where u can play as the best army against nazis in three major battles, moscow outskirts, stalingrad and berlin.

This land is my land - killing colonialists

Most multiplayer FPS/TPS games featuring the US will also have other factions that can fight them.

Counter Strike Global Offensive. Play Terrorists so you can stick it to the neocons.

Can't say I do, so I'll be watching this thread to find out about some. That said, the Sniper Elite games are pretty great in terms of killing nazis.

I mean it’s a bit of a stretch but in GTA 5 I’m like 90% sure that you kill U.S. soldiers in a mission in Fort Zancudo