What is the ruling on establishing a company in a Western country, where its transactions necessitate mandatory commercial insurance, given the significant difference in earnings between self-employment and a salaried job? Can this be compared to mandatory car insurance?

Yes, mandatory car insurance can be likened to corporate insurance. If something is permissible and a person needs it, and the state compels them to get commercial insurance due to the unavailability of Islamic (Takaful) insurance, then commercial insurance is permitted for them, and the sin falls upon whoever imposed it. The European Council for Fatwa (definition) and Research has issued a fatwa permitting commercial insurance in cases of legal compulsion, such as third-party insurance for cars, workers, and employees, due to the unavailability of an Islamic alternative (Takaful insurance).