Government troops attempted to arrest the drug boss on Monday, whose full name was Nemesio Oseguera Cervantes, in the western state of Jalisco on Sunday.
Oseguera was injured and died while being flown to Mexico City, triggering a violent reaction from the cartel.
Suspected members of Oseguera's Jalisco New Generation Cartel (CJNG) set fire to cars in several states and blocked numerous roads. They also attacked banks, petrol stations and shops.
According to the government, the situation was back under control on Monday.
"Mexico is calm," Mexican President Claudia Sheinbaum said.
"We woke up without any roadblocks and all activity has been restored."
The chaos raised concerns about Mexico's suitability as a co-host of the upcoming World Cup, which is set to begin in June.
A total of 13 matches are to be played in Mexico City, Guadalajara and Monterrey, with the rest held in the United States and Canada.
White House Press Secretary Karoline Leavitt said the US "provided intelligence support to the Mexican government," describing the cartel boss as a "a top target for the Mexican and United States government as one of the top traffickers of fentanyl into our homeland".
Sheinbaum stressed that only Mexican forces were involved in the operation.
"There was no participation in the operation by US forces. What we have is a lot of exchange of information provided by the US government, but the entire operation, from its planning stage, is the responsibility of [Mexico's] federal forces," the president said.
The Mexican Defence Ministry said eight gang members were killed in Tapalpa, Jalisco, during the military operation.
In addition, security forces seized armoured vehicles and weapons, including a rocket launcher that can shoot down helicopters or aeroplanes.
According to Mexican media reports, around 20 of Mexico's 32 states are affected by violence after the drug lord's death, including Jalisco, Michoacán, Aguascalientes, Tamaulipas and Guanajuato.
Several foreign embassies, including the German representation in Mexico City, appealed to their citizens to be cautious amid the unrest.
'El Mencho', a former police officer, had led the CJNG since its founding in 2011.
In the Mexican underworld, he was known as 'Lord of the Roosters' because of his fondness for cockfighting.
The criminal syndicate Oseguera led is a transnational organisation with connections as far afield as China and Australia.
In addition to trafficking fentanyl, it is also involved in extortion, migrant smuggling, theft of oil and minerals, and arms trafficking.
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