It wouldn't be a full scale invasion, it would start as a "counter terrorist operation" supposedly against cartels, but the ultimate aim would be getting rid of AMLO and installing a more reliable empire stooge. Mexico geopolitically has been a thorn in the side of the last 2 US admins, refusing to send money or weapons to Ukraine and normalizing with Cuba/Venezuela/Bolivia.

It does seem like a bad idea and a net loss for the empire, they don't really gain all that much from it but American senators are frothing at the mouth calling for it so there must be some interest or lobby pushing for it. Maybe they'll go fully mask off and re-create the Mexico-American war motives where it's just about annexing land and getting more of an impoverished non-white underclass to psuedo-enslave to expand their workforce?

some republicans have been braying about it, i think the casus belli is "cartels", but they really want more of an excuse to ethnically cleanse the southern US and kill immigrants faster

If Mexico becomes a less compliant client state, the US would see an interest in finding new ways to force compliance. Both the national security state and business interests will see value in this.

Whether that's actually invasion will depend on some historical developments, but the pressure is already there. Multipolarity is impacting Mexico like everywhere else.