I have to say I think it's always harder than it looks for people from different cultures to work together. The biggest mistake is presuming that, just because you're all working in the same language, you're all understanding each other. This is the case even when that language is native for everyone.
People migrating between the UK and the US can face some real obstacles in settling in, as they struggle to make themselves understood. You are more likely to forgive someone seeming awkward or difficult if you perceive that there is a 'language barrier', but if everyone has the same first language then no allowances are made for cultural misunderstanding. Error!
There are some good tips from Andy Molinsky here. From my own experience of helping people to adapt in a new working culture I would add:
1. Apply the benefit of the doubt. Always consider whether it's possible that the behaviour you have noticed (and aren't happy with) is a product of a different cultural outlook.
2. Take the time to get to know someone. If they're not already used to the working culture of the country you're in, chances are they've just made a big move. Take the time to find out about their life outside the office a bit.
3. Be open. If someone is coming off a little arrogant / quiet / bullish find a constructive way to tell them that's how it seems and see if there's a way you can help. It won't fix itself!
4. Consider some training. There are tools to help people flourish as they move from one working culture to another; getting the best out of both.