the overseas reviews for the film were very good.
but for some reason the over seas marketing was neglected almost to the last moment.
I assume the marketing budget is handled by the local distributor in each country. They would already have made their estimates, based on the previous ratios of domestic vs international.
that and for some reason trek movies just havent done as well overseas.
Keep in mind that ST III wasn't even theatrically released in much of Europe, which is why ST IV was marketed as "The Voyage Home: Star Trek IV" and had a little Shatner-narrated primer as to what had happened in II and III.