Like that matters. Besides it doesn't take a declaration of war to defend our borders, just takes determination which we don't have as your post illustrates.
“just takes determination”
That is the real bottom line.
The Military (and the Border Patrol) are capable, but political leadership calls the shots.
There is no way (legally) that unarmed border crossers can just be shot (summary executions). All that is really needed is a law authorizing immediate deportation of illegal crossers - flights right back to their home countries, after they are booked, biometrically identified, and heavily fined.