Mexicans sneak across the Border to get away from Mexico, but as we fill America with more Mexicans, we will become Mexico?

Honestly, I'd make your hypothetical about some of the other Latin American nations rather than Mexico. Mexico isn't as bad as a lot of people believe it to be, and many Hispanic individuals are actually just passing through there as well. The thing about America is that it's known to provide more opportunities and chances to get rich/live with comforts previously unknown, so they pass up Mexico. It also doesn't help that Mexico isn't tolerant of such illegals either, we're nicer in many respects.

Still, some parts of Mexico are as many people imagine, so I'll use that as a basis for my answer... and, clearly, I'd say that they'd flee to Canada. Canada isn't as harsh and the political climate there is also welcoming. Though, the actual climate is quite harsh, so we'll see many repatriate back to their countries of origin. It's not something unseen even today in the USA, when things don't work out for some.

Mike Adams, aka the Health Ranger, thinks that the idea is to kill the US citizens off with COVID shots, allow all the illegal immigrants to come in, because they will be very submissive and do everything the gov tells them to because they will be getting all sorts of free stuff and then they can rule them, always having all the Dem voters they want or need.  It will be totally communistic, very soon.

Better than full of racists like you.

What does a plague of locusts do after it has eaten the fields bare?

Not where I live.