Her mother was afraican, her father was american - she was born in america so carries citizenship there and has an US passport, but she is dual nationality by blood. If both her parents were Kenyan but they had taken her to the US to be born while they worked there or something, then that would give her a dual passport as well.
EU and Commonwealth citizens I would say should be a no to Excalibur if constructing it on the basis of UK members as it is lead by and founded on the basis of a hero and mythos who derives the strength of his powers (in the old days) from his proximity to the British isles. Captain Britain is a hero of the realm and as such the team should be comprised of UK heroes. It'd be nice if it were a citizen based team, like Alpha Flight - but I never had a problem with the multi national roster of the first line up. I wouldnt want a 'Premier EU Superteam' just cos everyone lumps us in the UK with the rest of Europe.
Brian, Pete, Meggan, Micromax, Chamber, Siryn and Wolfsbane would be a good line up. But the current one is just fine with me - it should be a team who has to work to form a cohesive unit. Not one of old friends who get along like a house on fire.