Nearly two weeks after Mexican forces killed notorious cartel boss Ruben “El Mencho” Oseguera Cervantes, questions remain about how the powerful Jalisco New Generation Cartel (CJNG) will respond and whether the blow will meaningfully disrupt the flow of fentanyl into the United States.

Carlos De La Cruz, a 20-year U.S. Air Force veteran who deployed after 9/11 and later served along the southern border, told Fox News the cartel leader’s death marked a major victory, but warned Americans should not mistake it for the end of the fight.

“When I say that this is a significant win, I mean it,” De La Cruz said. “El Mencho ran one of the most violent cartels on the planet.”

Oseguera, who rose to prominence in the post–El Chapo era, oversaw CJNG’s aggressive expansion across Mexico and into key trafficking corridors feeding U.S. drug markets. Under his leadership, the cartel became a central architect of fentanyl and methamphetamine trafficking and drew a $15 million U.S. reward for information leading to his capture.

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But De La Cruz cautioned that removing a cartel kingpin does not dismantle the organization.

“Cartels don’t collapse when you just cut the head off — they fracture,” he said. “And part of that fracture is going to see a lot of short-term violence while all these factions fight over territory.”

Following Oseguera’s killing on Feb. 22, the U.S. State Department issued travel alerts in multiple Mexican states, citing road blockages and criminal activity tied to security operations, underscoring concerns about instability in the aftermath.

Drawing on his military background studying enemy command structures, De La Cruz described the cartel fight as a long-term campaign requiring sustained pressure.

“You don’t win a war with just one airstrike,” he said. “The goal is dismantling the networks and going after their financing.”

De La Cruz, who is running for Congress and is the brother of Texas Republican Rep. Monica De La Cruz, argued that CJNG’s Foreign Terrorist Organization designation gives U.S. law enforcement and intelligence agencies expanded tools to target cartel infrastructure and financial pipelines.

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But he stressed that the fentanyl crisis should be viewed as a domestic security emergency, not a distant foreign problem.

“For decades, they were using their territories as launching pads to pump chemical weapons into America — because that’s exactly what fentanyl is,” he said.

De La Cruz, who said he worked side by side with Customs agents while deployed to the border, warned that cartel networks are highly adaptive and that any gains could be temporary without sustained follow-through.

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“These networks, they’re going to adjust. They’re going to adapt and they’re going to adapt quickly,” he said. “We have to continue to go after the money launderers, especially on our side of the border, because that’s the full fight.”

While Oseguera’s death removes one of the most dominant figures in Mexico’s criminal underworld, De La Cruz said the mission is personal.

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“I took an oath to defend this country,” he said. “And I intend to stand by that oath.”

Fox News Digital’s Greg Wehner contributed to this report. 

Stepheny Price covers crime, including missing persons, homicides and migrant crime. Send story tips to stepheny.price@fox.com.