The above scenario is absurd as you know it will never happen
Your list of countries would never allow a bordering nation to
a) build up hostile activity in close proximity b) overtly train and prepare c) intentionally feed misleading intelligence in order to conceal the above plans and objectives
Furthermore, your list of countries would never be stupid enough to have civilian festivities allowed to take place in proximity to any border directly next to, a training ground and force build up of hostiles
Hamas is a clandestine, guerilla organisation yet it managed to deceive the IDF, the Israeli govt etc etc
That will not happen anywhere else and pre emptive actions would be taken over time well before enough of a guerilla force could be raised to attack across a border
Your question 'what would they do?' is irrelevant because it will never happen
It is a ruse to 'create' a 'threat' narrative nothing more nothing less, to lump other western govts into the same basket as the Netanyahu regime, when we all know they are a rogue regime, totally devoid of accountability for it's own failure
The IDF and Bibi failed, they failed miserably.. and now the world pays
