If you want to measure the capital possessed by a nation, there are two ways of doing it. One is to travel the length and breadth of the country counting the houses, the bridges, the factories, shops and offices, and adding up their total value. The other is to knock on doors and ask people how rich they are. National statistics offices typically do both of these things, though not literally in this way.
The totals should be roughly equivalent, because however complex the chain of intermediation, it is the nation’s savings which fund the nation’s investment. The totals are not, however, exactly the same – for a few reasons.
For example, some national assets are owned by foreigners, and some household wealth is held overseas. But for large, developed countries the net effect of this is small because the two factors balance. The value of overseas assets owned by residents of Britain and of France is almost the same, in total, as the value of domestic assets held by overseas residents. Germany owns more than it owes, but the reverse is true of the US.