I feel like if this was the U.S. in Israel's position, opinions would shift differently, mainly because of the "say one thing, do another". Israel isn't expressing a regret for the loss of life while killing people, whereas the U.S. would totally be doing that to try appearing more sympathetic as the shellings continued. And it's not like the U.S. wouldn't do this if the cartels really took over Mexico and began threatening our borders with levels of violence that would make Hamas look sweet.
Seriously ask the question: what if the Cartels took control of Northern Mexico, and the central government could do NOTHING to stop them, and even maybe brought them into their government to "control" them a bit? And then they started lobbing mortars over the border. Or missiles that could hit all of Los Angelas. And any other cities with 200-ish miles of the border. What would your government's response to this be? What would your PEOPLE demand the response to this be? And throw in the idea that Mexicans might see most of California, New Mexico, Arizona, and Texas as "theirs" and "stolen" by Americans in the Mexican-American war, and want a "right of return" even for descendants of refugees? And remember, they're firing the missiles from Churches, Schools, and Hospitals, almost-exclusively, so if you want to destroy the missiles, you MUST kill innocents too.
Way to parallel? Too much? TOO BAD! That's a disturbingly-close parallel to what is happening in Israel. Except the fighting has actually started.
TLDR: If 200+ miles of the USA-Mexico border was getting rocket attacks constantly, with tunnels & human shields being used, what would you advocate for your government to do?