Currently it is not possible. Unless its proceduraly generated. But then see: “No Man’s Sky”.
Earths lands surface it 150 000 000 km2. Lets say you go for 1/100th of that. It is still 150 000 km2.
Lets assume that one square km map piece would be around 100mb (realistically i think it would be at least double of that).
You are facing 100 000 000 * 150 000 bytes for just map data. That is 1.5 TB for just map (if i counted zeros correctly).
And its data you need to produce/download/upload etc. Game Engine also needs to swap it around in realtime.
Another factor is (unless you want to make **** like no mans play) creating content for such huge world. ! sq km is comparable to huge map from shooter games.
Are you ready to make 150 thousands of such maps, then sell game for 99.99$ ?