Far more people in this country care about the wedding than these tornadoes; it's simple ratings.
And CNN, for example, has spent big money moving their whole staff to London.
What's really unseemly is when they are in London interviewing Dame Edna or some fashion designer and laughing it up and then the anchors have to turn around and do their frowny concerned face to talk about the tornadoes.
And there is a regional component; 200+ killed in NY or LA and they'd drastically cut the wedding coverage.