I’ve never been happy with how Bing handles geo-location detection of web sites. They use and rely mostly on the meta language tag to determine if the site should be in Bing US versus a localized version of Bing. Google’s Matt Cutts somewhat mocked how Bing handles this by saying:

That being said, this is how Bing handles it and if you see your site in a regional Bing that doesn’t make sense, you can change it by updating your meta language tag.

Brett Yount said in a Bing Community thread that once this is updated, Bing should update your site within one or two crawls. Brett said:

Change that and the issue should be corrected within one or two crawls.

So overall, if your site gets crawled once per day, you should be fine within a couple days.

Forum discussion at Bing Community.