No, it's not uniquely japanese. Most civilized countries remove their shoes when entering homes. For example I live in Russia and we also remove our shoes when entering houses. Your confusion arises because you try to compare Japan with the US which is a uniquely barbaric and underdeveloped nation, so they go everywhere in their street shoes.This custom has no spiritual meaning at all and is directed towards hygiene instead. When paved roads were a luxury (so, basically whole our history prior to XX century) it was important to keep the dirt out of the private part of the house.
the map is misleading. It does not have topographic markings, so we don't know the height. Most shrines and other cult objects were placed by primitive ancient people to be higher up, "closer to the skies". That's why most of the shrines have 'prominent' locations which are higher than the tsunami-induced water level. Besides, many eastern plains such as Kanto plain, formerly were much lower and were raised artificially, so maybe back then those shrines were actually located near the shore.
これぞ、奇跡ですね
の神功皇后はジングウ皇后と読みますよろしくお願いします。
