What is the ruling on working and studying in a hospital predominantly run by Jews in Canada, and is studying in non-Muslim countries considered a necessity for obtaining better training?

The basic principle regarding travel to the lands of the disbelievers for worldly purposes is prohibition, due to the fear of religious harms. Exceptions are made for necessities, such as medical treatment or acquiring a specialization needed by Muslims that is not available in Islamic lands.

For example, studying medicine in Canada is not considered a necessity. This is further emphasized when we know that Jews do not readily share their good expertise with Muslims, and if the virtue of training there is compared to the risk of corrupting one's religion and morals, we find that the harm outweighs the benefit. The jurisprudential rule is: averting harms takes precedence over acquiring benefits.

As for working in a Jewish hospital for training and gaining experience while guarding against the harms of mixing with them, it is permissible as long as it does not lead to a religious corruption. The Companions (may Allah be pleased with them) used to trade with Jews and work for them for wages. Scholars have permitted acquiring beneficial worldly expertise from disbelievers. However, among the religious harms of working in a hospital in Canada is the expectation of being affected by the corruption of the religion and morals of the people of those lands, so this should be noted.

If the questioner can preserve his religion, maintain righteousness, connect with Islamic centers, and cooperate with them in calling to Allah, then let him persevere in that and seek Allah's help in succeeding in his mission. But if he fears for his religion and finds nothing to help him remain righteous, then there is no doubt that his religion is the most important thing he must protect, so let him hasten to migrate to the land of Islam.