Is it permissible, Islamically, to conduct the marriage contract twice: once in the wife's country and again in the husband's country, given the difficulty of the families gathering in one place to conduct the marriage?

What was mentioned does not prevent the marriage contract from being performed once. It is possible to appoint a proxy for the marriage or use modern communication methods. There is no need to perform the contract twice, as it would be redundant, and there is no necessary connection between the marriage contract and inviting family and friends.