Is traveling to and residing in Algeria considered disobedience to parents who do not pray, while the family remains in France, and should one stay with them to guide them?

There is no harm in traveling for a legitimate purpose, and this is not considered disobedience if it does not cause harm to the parents. It is obligatory to honor one's parents and maintain kinship ties, and this includes enjoining them to good and forbidding them from evil, especially urging them to establish prayer and warning them of the consequences of abandoning it. A Muslim is advised to reside in Muslim countries to avoid the dangers of disbelieving lands to one's religion and morals.