Unfortunately, that is the one type of app that does not really exist for mac. There is Route 66, but it is a horrible app -- hard to use, ugly, etc. I have been searching for an app like DeLorme Street Atlas, but to no avail.
Having said that, if you are using GPS coordinates, etc., you might try Route Buddy. Not the same as the DeLorme, but can find coordinates.
Good luck! (Actually, I am hoping somebody will post some updated info on a new app - but not holding my breath!)
The best alternative to the Mappoint is the Badger Maps, you can download in on you iPhone or iPad and export your data. I've been using it for a while and fits all my needs. It helps me to optimize my routes, to find new leads, and to save time. You should give it a try
I didn't use Mappoint, but I used to use Streets and Trips which was very similar. Since they've discontinued, I've started using Badger Maps and I personally think it's superior, especially for the type of work that I'm doing. I use map software to route my trips for daily sales and coloring different places on my maps.