AdSense default has an average of about $8 CPM for English channels in North America. All networks use AdSense as a base and have the potential to augment it beyond that but most channels never see additional ads as those go to the big channels first and rarely does it trickle down.
CPM is entirely based on your audience. No advertiser cares about your channel or your network. Rather, they target certain demographics of people. Gender, location, interests, the type of content they're searching for, etc. As a result of this, moving from one network to another won't in most cases alter your CPM in a meaningful way. Networks don't "have a cpm". If there aren't advertisers looking to put their content in front of your audience, then you will have a poor fill rate and likely a poor CPM.
