They will have a problem with this, as the US armed forces is mostly southerners from conservative states. And, Texas alone has a large membership of national guard, state guard, and militias. Keep in mind that the border enforcement currently being done by the Texas DPS. Federal forces down here are few and far between.
I am not doubting your for one second, who knows how this will turn out, it could all fizzle out or morph into somthing really crazy.
Look at how the Federal Government overplayed 1/6, how do you think they would respond to National Guard troops on the border, sent there by Republican Governors from all over the country.
The Biden Administration’s response is hard to imagine how far they will go.