The largest mall in the U.S. is Mall of America near Minneapolis.

http://en.wikipedia.org/wiki/Mall_of_america

It has around 500 shops so the one in Saitama is huge even if not larger in square footage, and I don't think Mall of America is one km long.

In order to blend into the community, new malls tend to be smaller and has a conventional "main street" and garages hidden behind the store front. The best examples is the Santana Row in San Jose and The Washingtonian Center in Gaithersburg near Washington.

http://www.shopwashingtonian.com/
http://www.santanarow.com/more/about/partnerships/

Japan not using cars is not entirely true. I went to see a friend who lives in Saga. They drive everywhere. They may use much smaller cars and trucks but they use motorized vehicles nevertheless. I has in Japan two weeks ago right in the middle of rice harvest and I saw combines everywhere. Tiny ones but combines nonetheless. Only a few small plots were being hand harvested.