I see many videos on youtube where they tell you to get residency visa in countries that are unlikely to be involved in a world war 3.
What are you talking about? WW3 never had happened and even when it have to maybe sometimes in the future, the USA will fully be involved.
Perhaps having USA for instance, they were heavily involved in the past WW and still, residency visa is required for a non-immigrant with temporary purpose of staying in the country.
It is just a legal permit for foreigners to have access to service and limited facilities at their period of short term staying.
Is it really enough to have a residency visa? I think the country you are a citizen in can still force you to come back to join the war if they want to.
Ars you referring to civilian or military citizens who went abroad on a temporary purposes? It might be legal practice for the military but doubt if it is practicable with just a common civilian who can not even defend themselves.
Infact, fighting for a country is not the duty of the entire citizens but governments and the militaries.
So your country forcing you to come back home from a sovereignty country like the US where you have a legal residential permit can be termed a violation of the international law.
I think the only way to avoid such a situation is by getting citizenship in a country that is unlikely to join a war, so residency is not enough.
And it might not even be enough with dual citizenship. Because the origin country could change the law and forbid dual citizenship and then the country you got a dual citizenship at would have to remove your citizenship and deport you. So you would have to renounce your citizenship with the country you think is likely to join a war.
If you are referring deportation of the country where you resides with temporary or indefinite residential visa, during time of crisis that may prompt that action, of course foreigners are liable to fall back home while governments interests is focused on protecting their citizen's either by indigenous, immigrant visa or green cards to obtain permanent residency.
So constitutionally, you have been ordained dual citizenship.