After Hurricane Harvey has caused widespread devastation in Texas and Houston, the Mexican government has offered to "help" (link):

Mexico offered to help Texas deal with the disaster, "as good neighbors should always do in trying times." ...On Sunday evening, Foreign Minister Luis Videgaray and Texas Gov. Greg Abbott spoke by telephone. ...Carlos Gonzalez Gutierrez, the Mexican consul general in Austin, said he has been in constant communication with the governor's office to determine how Mexico can best help. ..."As we have done in the past, Mexico stands with Texas in this difficult moment," Gonzalez said.

If, say, Canada offered to help they'd mean it. They might want something in return, but they'd be generally sincere. The Mexican government isn't sincere: their only concern is their own interests.

We should cooperate with the Mexican government on such things as disaster response affecting the border, Mexican nationals in Houston who need disaster relief, and so on. However, the other "help" they'd provide would come at a great cost.

After Katrina, the Mexican government also offered to help. You can read about that at the link. Illegal aliens flooded into New Orleans to do rebuilding jobs, displacing native workers who should have been doing those jobs. All of that was done with the help of the George W Bush administration, which allowed connected contractors to employ illegal labor through subcontractors. Meanwhile, Americans who should have been doing rebuilding jobs were sent to other cities. Instead of working, many were on public assistance. We don't want to rely on natural disasters to get people off public assistance, but when the opportunity presents itself it should be taken advantage of. What Bush did instead was a great deal for crooked contractors, foreign citizens, and the Mexican government. It didn't serve the interests of most Americans however.

As a result of Mexico's "help", they were able to establish yet another source of political power and money inside the U.S. Mexico had closed its New Orleans consulate in 2002 but reopened it in 2008 due to the influx of their nationals after Katrina [2].

Then as now, the Mexican government will rely on leftwing leaders inside the U.S. to help their efforts. Those leaders - Democrats, the media, etc. - will turn their backs on Americans who should be doing rebuilding jobs and push Mexico's agenda. They'll smear opponents, ignore the downsides of the "help" Mexico offers, and so on.

Unfortunately, given how weak and unpatriotic Donald Trump is, he might fall for Mexico's offer. Trump's base might throw a brief tantrum about Mexico's offer and then they'll be distracted by something else. Or, the things they say will be used by Mexico's de facto allies inside the U.S. Their leaders - such as Breitbart News writers - will present accepting Mexico's "help" as a liberal thing, when liberals should be its fiercely oppose accepting that help due to its impacts on American workers.

Rejecting the nefarious aspects of Mexico's offer requires a smart, rational, patriotic, dedicated, big tent opposition. That would involve working to discredit any leaders who turn their backs on American workers, engaging the media on the downsides of the offer that they won't mention, and so on. Given that today's environment is even worse than it was in 2005,, it's hard to see such an opposition materializing.

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[2] nola . com/news/index.ssf/2008/04/mexican_consulate_opens_monday.html