So for this file, I’d agree with you that reducing both the overall area of the contours to convert to a mesh and simplifying the contours will help speed things up.
In CAD, I drew an area around lot 13 with plenty of extra room on all sides to help guide me later in SU for what I need to keep and discard. This could be done first in CAD but if the lines are all joined, then you’d have to trim or break them so I figured it’d be easier to do in SU. Either way is fine.
Here is a comparison of mesh made with just Sandbox Tools (Toposhaper works with point clouds, etc but since you have clean contours, Sandbox works just fine). Note that there are over 65,000 edges for just contour linework in this new reduced lot 13 area. After using Simplify Contours extension, the number drops to 3,200. The Sandbox meshes look nearly identical.
Lastly, with hidden geometry turned on, you can see the density of linework needed to create each mesh with the original CAD linework being overkill.
Countours_Lot13_Simplified.skp (1.2 MB)
Edit: for Google Earth, just use the ‘Add Location’ feature in SketchUp and move your mesh to align with it’s real-world position. Then turn off any layers you don’t want to show in Google Earth and export as KMZ format. Tip: sometimes the Google Earth terrain and SketchUp mesh overlap each other so I tend to ‘fake’ it a bit and move my mesh up about a meter or so so that it ‘floats’ just above the Google terrain.