It's close but on balance it would have to be the Anglosphere. We are obviously in Europe and socially and politically we're much more of a European country than we would like to admit - and I have a feeling that if French or German was the world language, we wouldn't have such a problem accepting that fact. However, the Anglosphere, particularly the non-US Anglosphere, is basically a result of Brits and Irish people transplanting themselves into various parts of the world at various times and taking a few immigrants from other places with them - there are differences but it's culturally much closer to us than anything else is, and we engage with it a lot more because it speaks the same language as us. This goes far enough that I wouldn't really consider people from some parts of the Anglosphere (Australia & NZ, Ireland) to be foreigners.