This is not the case. The US intelligence has been deploying forces in Latin America against cartels for long long time.
Mexico withheld permission for American military and intelligence deployments from 1990 to 2025 (DEA and other law enforcement was allowed), but they changed recently.
> The parent claimed that this has never happened before because it would have been considered an act of war.
Because it has never happened before in Mexico. It has been political suicide to even consider allowing foreign troops in Mexico because of the memory of the French Occupation.
You cannot treat "Latin America" as a monolith. Each country has a different sociopolitical background and history.
[0] - https://www.southcom.mil/About/History/SOUTHCOMs-60th-Annive...
But let's not fool ourselves. These are American operations taking place in Mexican soil (with the cooperation of the Mexican forces of course, it was not an attack against Mexico).
All including dea with intel and actual boots in Mexico.
The semantics comment was on the point that this is not technically the US military. Sure it is not the military it just has access to its personel and equipment.
It does not have access to the same equipment or (more critically) personel - especially in intelligence, as intelligence ops were not allowed either until the Sheinbaum admin.
Also, the Colombian Cartels are a different set of organizations that have different origins from the Mexican Cartels - the former being a side effect of the Colombian Civil War and the latter being a side effect of the 1990s Peso Crisis and the mass layoffs in the Mexican Army and Petrochemicals industry
Read or watch "100 Years of Solitude" by Gabriel García Márquez. The fissures of the 1899-1903 Colombian Civil War (4-10% of Colombians died) were never resolved and it morphed into "La Violencia" which then morphed into the ongoing Colombian conflict.
You need money to buy weapons, so Colombian insurgent groups (right and left leaning) entered the drug trade to arm themselves - especially after the USSR reduced funding in the 70s-80s to concentrate on Afghanistan.
You see the same dynamics in Afghanistan, Syria, and Myanmar.