Some amusing things regarding this topic include
Nuclear bombs now weigh less than 15kg or 33lb and can fit into backpacks.
The majority of the worlds items are transported in shipping containers almost all of which go unchecked into the U.S.
The northern boarder between the U.S and Canada is virtually unguarded.
If you want people to stop bombing you there is a very simple solution, dont bomb them first, ecomically exploit them, support their puppet governments, instate their puppet governments and stop giving hundreds of billions of dollars to Israel.
OR
Just attempt futile measures that will only annoy graffiti writers while pretending to make the nation secure.