Well you are correct that killing attempted border crossers is the only practical solution, both in the US and in Europe.
In the case of Italy and the UK, they should be sinking the boats carrying “refugees”, and seizing and then sinking the mother ships.
The US should not (in my opinion) utilize killing force until the border is closed and militarized such that thousands of people are not crossing every day. Killing the 10-20 who get through a properly fortified border? Fine by me.
Killing 12000 people a day who have no idea what they are facing? My preference is to make it a lot harder to enter the kill zone first.
And, by the way, this will involve land seizures from Americans whose families have been on that border since the Alamo to create a death strip of sufficient depth.
The East German design kept folks IN; I'm sure the same could be used by us to keep folks OUT!