What is the ruling on a white marriage with the intention of divorce for the purpose of immigration, and what is the ruling on traveling to a country where one fears not being able to maintain the hijab?

The regret and remorse you feel are a sign of your awareness of having erred, and they are an impetus for repentance. Among the conditions of repentance are ceasing and refraining from the sin. Therefore, you must stop this action and abandon traveling to those countries where you cannot practice the rituals of your religion and maintain your hijab (definition) and chastity. Repent to Allah with sincere repentance by abandoning that sin, regretting it, and resolving never to return to it. Know that whoever gives up something for the sake of Allah, Allah will compensate them with something better, and whoever fears Allah, He will provide for them from where they do not expect. So entrust the matter of provision to Him, and if you are in need of work, seek it in your own country.