Is it permissible to consider marrying a Syrian girl and to avoid marrying a Tunisian girl, due to two previous failed experiences, and what is the legitimate way to get to know her and marry her given the long distances?

The Wise Legislator [Allah] has urged the selection of a religious woman. A difference in nationality does not legally prevent marriage. One can utilize reliable websites that assist in searching for wives. If you do not find a wife from the desired country, search for a righteous one in your own country, and seek help through supplication and by relying on trustworthy relatives and acquaintances. Marrying women from your own country may be preferable due to the compatibility of temperaments and customs. Do not regret what has passed, for Allah Almighty knows what is best for you.