I am of the opinion that you don't have to qualify for Crufts, you just enter; although, that may not be the case for foreign dogs. I'm not sure about that. It wasn't until relatively recently that foreign dogs were eligible, so maybe there is a limit, or qualifications of foreign dogs allowed.
I've been told that people in England who don't usually show their dogs, enter Crufts.
If you live in the US to qualify for Crufts there are only two qualifying shows - the National Specialty (for each breed) and Eukanuba. BOB, BOS and BBE at each of these shows qualify and are invited to Crufts. So no it's not that easy and not many dogs are actually qualified. There are also qualifications for dogs in the UK but I do not know the specifics of those. UK Show Champions are qualified for life.