I'm not in the US, but it does seem a little high.
I find that Network admin is a bit of a vague term these days especially with smaller companies.
In my opinion the Network admin should technically only be in charge of the Network infrastructure.
To give you an example, I do network support for a number of large companies and most of them break job roles up as follows.
Network admin - Network Infrastructure, switching, routing, wireless
Security admin - WAN and LAN security, Firewalls, IPS, IDS, NAC etc.
Systems admin - Domain controllers, servers etc.
Database admin - Self explanatory.
and the list can go on. but in smaller companies you my find that the "network admin" does all of these things.
Even if you just do two of those things, for instance Network Infrastructure and Network Security, it has to be taken into consideration.