I've often heard conservative Christians repeat a commonplace that goes something like this: "When a nation, or even its leader, blesses the Jewish people, God will bless that country." I have heard it applied to the UK as well, that when a British Prime Minister like Lloyd George or Margaret Thatcher supports Israel, the UK does better. Or that Britain led the world in supporting Jewish people throughout the 19th Century, which resulted in British hegemony around the world.
The same has been said about the USA. George Washington insisted that Jewish people receive the full legal rights of any other American, and as a result, America achieved independence and flourished. Twentieth-century influence and prosperity has also been credited to the United States' positive policies toward Israel and freedom for Jewish people.
The scriptural foundation for these assertions come from Genesis, where the Lord says to Abraham, "I will bless those who bless you, and him who dishonors you will I curse, and in you all the families of the earth will be blessed" (12:3). This promise to Abraham is understood to apply to all of his descendants.