As you probably know, the USA has been a strong ally of Israel for decades, not only monetarily (Israel, in spite of being a rich country, is the USA's main recipient of monetary aid) but also militarily and diplomaticaly.
Many important Jewish organizations -financed mostly by American Zionist Jews- try to lobby to maintain this good relationship between Israel and America and, I must say, they've been quite successful at it. Now, if you wonder how does this 'lobby' works, it's through a lot of means (from PR
to to "educational chats") but mainly and most importantly through money -cash directed to political campaigns of those favourable to Israel and cash directed to the political campaigns of those who are competing against the ones critical of Israel. Of all these, AIPAC, American Israeli Public Affairs Comittee, is by far the most relevant.
I'll give you some quotes:
"...better than anybody else lobbying in this town ... You have been stunningly effective."
Former US President Bill Clinton
"You are the most effective general interest group…across the entire planet."
Former Speaker of the House Newt Gingrich
"Fully three-fourths of America's foreign aid budget is devoted to Israeli security interests is a tribute in considerable measure to the lobbying prowess of AIPAC and the importance of the Jewish community in American politics."
Benjamin Ginsberg, prominent conservative lawyer and political commentator
"Congress is 'terrorized' by AIPAC... In practice, the lobby groups function as an informal extension of the Israeli government."
Congressman (1961-1982) Paul Findley
I asked Rosen [Steve Rosen, at the time Research Director of the organization] if AIPAC suffered a loss of influence after the Steiner affair (a scandal over spy allegations for Israel). A half smile appeared on his face, and he pushed a napkin across the table. “You see this napkin?” he said. “In twenty-four hours, we could have the signatures of seventy senators on this napkin.”
Jeffrey Goldberg (The New Yorker).
"I think Israel is especially lucky that AIPAC exists in this country to present Israel's case."
Former Israeli Prime Minister Benjamin Netanyahu
"So great is the perceived power of AIPAC to mobilize financial support for pro-Israel candidates or to challenge those perceived as hostile, that this year , as is usually the case, around half the members of the Senate and one-third of the House of Representatives were expected to attend the policy banquet at [AIPAC's annual] conference."
Martin Sieff, Managing Editor of International Affairs, United Press International, 1999.
"Thank you for being here. AIPAC's work on behalf of America and Israel is valuable and important. With friends like you, Israel, and American interests in the Middle East, are well served. Thank you."
Senator John McCain June 20, 2001.
"This reluctance to criticise policies of the Israeli government is due to the extraordinary lobbying efforts of the American-Israel Political Action Committee and the absence of any significant contrary voices."
Jimmy Carter, former president of the USA
"All the Jews in America, from coast to coast, gathered to oust Percy [Charles Percy, senator for Illinois who supported the sale of planes to Saudi Arabia]. And the American politicians - those who hold public positions now, and those who aspire - got the message". - Tom Dine, former executive director of AIPAC
According to the study of JJ Goldberg, around 45% and 25% of the funding of the Democratic and Republican party respectively came from pro Israel Action Groups. Given that those two parties control the nation, it's no wonder to realize why America has adopted such a pro-Israel stance over the years.