Perhaps. You have to consider how your product is used and how the users will sensorially interact with it. If you have a website, for example, you could probably assume similar US and UK usability -- but now consider layout for Semitic languages which are read right-to-left -- or consider ideographic languages where the ideographs could interact with other graphical elements in a way wholly irrelevant with the languages you're familiar with.

If you have a physical product, the question is conceptually the same, but the actions are different. You have to consider how users in a given culture use and interact with products of that sort. Different cultural memes, ways of learning and expectations can effect usability.

There are some simple ways to do these things if you have a small budget. You could easily go to craigslist and recruit 10-15 natives of a given country or region. Give them the product or have them use the website (for 60-90 minutes), video it (with their permission of course and for reasonable compensation), and you'll get a potentially useful indicator of usability. If you're P&G or Microsoft, you've got the budget to test against statistically valid sample sizes pretty much everywhere in the world. You don't have that, so you need to use some heuristics.

Good luck to you. Should you have any questions, I'd be happy to discuss.