By Luca: https://central.tri.be/issues/92811#note-8

functions.php

<?php

/**
  * @link https://theeventscalendar.com/support/forums/topic/event-aggregator-event-country-imported-from-facebook-in-wrong-language-2/
  */
add_action( 'tribe_aggregator_before_insert_posts', 'test_listen_for_event_creation' );
add_action( 'tribe_aggregator_after_insert_posts', 'test_stop_listening_for_event_creation' );

function test_listen_for_event_creation() {
    add_action( 'tribe_events_venue_created', 'test_translate_venue_country', 10, 2 );
    add_action( 'tribe_events_venue_updated', 'test_translate_venue_country', 10, 2 );
}

function test_translate_venue_country( $venue_id, $venue_data ) {
    $country_map = array(
        'Germany'     => 'Deutschland',
        'Switzerland' => 'Schweiz',
    );

    if ( isset( $venue_data['Country'] ) && array_key_exists( $venue_data['Country'], $country_map ) ) {
        update_post_meta( $venue_id, '_VenueCountry', $country_map[ $venue_data['Country'] ] );
    }
}

function test_stop_listening_for_event_creation() {
    remove_action( 'tribe_events_venue_created', 'test_listen_for_event_creation' );
}