i). Probably this does not contain anything to religion, rather this is governance system in both countries, which defines who is to become its President or who is to get nationality etc.

ii). KSA Government is a monarchy since its creation with rules to be defined as per the tennets of Islam ( to be more specific as per the Wahabi /Salafi school of jurisprudence). There is no specific written constitution for the country. Since it is a monarchy lead by family of Saud, King is supposed to be from this specific family and he is the head of all the important pillars of state like legislative, executive, and judicial functions etc. Moreover, key ministries and governorships of its provinces are generally reserved for royal family.

iii). On the other hand, USA is federation republic/representative democracy. Its government structure comprise President, Cabinet and Congress (Senate and House of Representative). The President is elected through indirect electoral processe etc.

iv). KSA can only be consdired as centre of Islam because of holy places lying in it, otherwise it has nothing much to do with islam or muslims.... Moreover, monarchial system was there in Islam from Ummayads onwards and it may not be prudent to term USA government more linked to islamic systems only on the basis of the reason of a black man becoming President, or having nationality thing for all and sundry or giving much human rights.....

__________________
'Thee woh ik shakhs kay tasawar saay - abb woh ranayee khayal kahaan'