Is it obligatory for me not to cut off everyone I know for more than three [days], even if they are in different countries, and if that is difficult for me?

A Muslim is not obliged to speak to or message everyone they know or see, nor are they obliged to seek them out and inquire about them, unless they are relatives (Araham), in which case they are obliged to maintain kinship ties (Silat al-Rahim) to the best of their ability. As for the prohibition of shunning a Muslim for more than three (days), it applies specifically to those who are in dispute, or to someone who meets their companion but turns away from them and does not speak to them out of avoidance. This is indicated by the Hadith (definition): "It is not lawful for a believer to shun a believer for more than three (days). If three (days) pass, and he meets him, he should greet him with peace. If he returns the greeting, they both share in the reward. If he does not return it, he has incurred sin."