I do agree with you that US foreign policy is NOT exclusively controlled by Israel but Israel's supporters (or Israeli lobby) wield considerable sway when it comes to formulating US' middle east policy. Israel also enjoys a very strong bipartisan support from the US lawmakers - who can be pretty hawkish in support of Israel with an eye to woo the wealthy jewish supporters to their side without risking any consequences of their stance other than a steady flow of cash to their re-election campaigns.
If you look at it - historically the Democrats were closer to Israel and to the jewish voters (they still are to most liberal/progressive upper middle class jewish voters). What happened over the last 3 decades is the phenomenon of Evangelicals gaining a lot of strength within the Republican party. This, coupled with the new found love between the Evangelicals and the state of Israel, explains the immense and hawkish support that Bush and every other Republican presidential candidate has shown in the recent years.
Israel and US relations during the Obama years have been the most frosty since I believe Carter was president. Liberal/progressive jews may love Obama and will vote for him but a vast majority of right wing jews loathe him. They think that he has turned his back on Israel and left it alone to deal with the threats in the middle east.
I don't know if I completely agree with you that Republicans gave a shut up call to Israel on a pre-emptive strike on Iran. May be you would like to provide some sources for that. I think that the neo-cons(most of the leading ones are die-hard Israel supporters) who cooked up the whole idea of attacking Iraq had carefully laid out sequence of actions to tackle and further US' interests in the region. The problem is that their calculations and predictions didn't match the reality on the ground and the aftermath of Iraq invasion was pretty ugly. Of course Bush could not stomach another misadventure when Iraq was blowing up all over. If Iraq had gone over smoothly or as expected then I think that they MAY have gone for a strike on Iran with or without Israel's coaxing. During Bush years a lot of covert effort was made on ground work to create a favorable environment for the next move. Some of it showed up during the protests in Iran after the 2009 elections.
Obama's foreign policy is complete opposite to Bush's doctrine. Some would argue that Obama has continued Bush's policies. I think he is a realist and not a very dogmatic president as some on the right would like him to be portrayed. He is a realist and a pragmatist. With the way things were going he had no choice but to continue the same policies to have continuity in a war that was started by his predecessor. I believe that Obama will not go to war with any other country with the economy in shambles and none of the allies having the stomach to support another war so soon.
We have to look at whats going on on this front in the context of American elections. To quote James Carville, the brilliant Clinton advisor, its the economy, stupid! Romney knows that with his non-existent foreign policy experience he can't beat on this front specially when Obama has kept America safe and achieved the ultimate trophy by killing OBL. Romney will try to avoid to make this election about foreign policy as he knows that he will lose out and if the polls are any indications than he is doing the smart thing.
The reality is that with the economy in the dumps and with the public opinion strongly against ANY other foreign invasion I don't think that ANY president - Obama or Romney would like to get involved in any military confrontation with Iran at this time. Even if Netanyahu keeps at it the US president could always use the counter arguments by the Dagan and other significant voices from within Israel.
Everyone is feeling the pinch economically in this global economy and given the fluid situation in the middle east an attack on Iran could result in some unintended consequences. We know that Turkey is strongly against an attack on Iran - you rightly mentioned that Russians and the Chinese absolutely don't want it. People talk about Arabs supporting it but I don't think that other that Saudi Arabia any other Arab country which wants an attack does really matter. None of these Arab countries have openly advocated an attack yet the western press does slip in references about their desire to see that happen - not sure if its the reality or part of a propaganda campaign.
Some Israelis officials or politicians, I can't specifically who, have made statements saying that according to their calculations if they attack Iran the retaliation would be bad and would continue a few weeks but would only result in 300-400 casualties at the most. The emphasized that this is what most of their simulations are showing them. I am sure they are quoting the best scenarios as I believe that a conflict with Iran would definitely result in some serious unintended consequences.
@Tutor
This is such a fine post mrk123, a template for how to make meaningful contribution to forum. I will reply at length (which will take a while, so my preemptive apology :P)