Judges in the US are allowed to judge based on their accredidation, and more importantly on their visibility in the dance world - the pay is the same for a nationally known judge and a local guy, so most comps use the 'big names'. For instance, you can't judge Championship level dancers unless you have Championship credentials.
DVIDA is an organization based out of a dance retailer's website, so they are not taken to seriously at all. My guess is that selling certifications ranks along with dance videos and dancewear with these folks!
Look at who judges and teaches the students at the kinds of competitions you want to aspire to.