It is a significant result, but other parts of the poll are quite a bit better for Israel than the haters want you to realize.
Some other results:
75% of Americans have a favorable opinion of Israel - a steady rise from 47% in 1992 (although in 1991 there was a huge bump for Israel during the first Gulf war, the only year that more than 75% of Americans had a favorable opinion of Israel - for not defending itself.)
64% of Democrats have favorable opinion of Israel, far more than the 38% who have a favorable opinion of the Palestinian Authority. This is most definitely not something that Mondoweiss or IfNotNow wants to trumpet.
If you look at enthusiasm, the people who love Israel (very favorable opinion) outnumber those who hate Israel (very unfavorable opinion) by 26%-6%. This is opposite to the Palestinian Authority, where only 5% love it and 24% look at it very unfavorably.
As Gallup summarizes:
Israel enjoys an enormous advantage over the Palestinian Authority in Americans' favorable ratings toward the two groups. Against that backdrop, Americans are also inclined to say they sympathize more with the Israelis than the Palestinians in the Mideast conflict. This aligns with decades of U.S. foreign policy that has stood by Israel at the United Nations and with foreign aid.
So when the haters cherry pick one statistic from many, it is important to remember that the United States remains very pro-Israel - and in some ways it is the most pro-Israel it has been in three decades.