Accepted answer

I'd guess its a projection issue. The co-ordinates in the topojson and your center look like they are WSG84 or Mercator co-ordinates (the America's are expressed as negative longitudes) and they are similar to the coordinates in this question. WSG84 is generally a safe guess for projections particularity for things like Google Maps, although Albers is commonly used for North America.

I've made a gist using Mercator which displays the map and you can see the block here.

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