As the US midterm election results rolled in, long-held Israeli assumptions about the transatlantic alliance began to shatter.

"For us in Israel, this will be a generational sea change," wrote one prominent journalist in Israel's biggest-selling newspaper, right-leaning Yedioth Ahronoth. "The [prime minister, Benjamin] Netanyahu government sowed the wind and reaped the tsunami." Israel's opposition leaders have lined up to blame their prime minister, with one saying the US results showed "just how toxic Netanyahu has become" among both Democrats and Republicans. The prime minister himself has so far remained silent.

"Israel's political establishment understood intellectually that things have been shifting. They have not understood how much and how quickly," one US official with knowledge of the situation told me. Israel's relationship with the US was a campaign issue in races across America.

Many Democratic candidates were sharply critical of Israel's actions in Gaza and the occupied West Bank, and the costs of the joint US-Israeli war on Iran was a key issue for many voters.

The US president himself blamed the Iran War for the Republican rout – a war that Israel's leader is widely seen as having promoted to him.

And US Vice-President JD Vance cited the US relationship to Israel as one of four key reasons voters had deserted the party, hammering home the message that the relationship is now seen as a political problem by its key ally.

"That might be even worse than what happened in the midterms," Israeli political and security analyst Yaakov Katz told me. "Because the Democrats we knew about, now [Vance] is pointing the finger and saying: 'Our voters want us to change our position on Israel' – and Israelis don't fully understand where this is going." The question plaguing Israelis now is what this means for Israel's security and influence.

The sense of staunch US military and diplomatic support had remained unshaken in Israel despite growing anger among US voters, President Donald Trump's public insults to Netanyahu, and differences over Israel's actions in Iran and Lebanon.

Israel's prime minister continually boasted of his closeness to Trump, describing his "true friendship" and "unwavering support".

And just nine months ago, Israelis watched their armed forces wage war on Iran hand in hand with the US military, as the "unprecedented" coordination of the two allies became a daily mantra among military spokespeople and politicians.

So Trump's unexpected statement during a Fox News interview this week that he would stop $3.8bn (3.4bn euros; £2.8bn) in US military aid to Israel two years earlier than planned, caused shock here – not so much for the loss of aid as for what the move said about Israel's status as a diplomatic partner. Israel's president said the announcement came as "a bolt from the blue".

"Nobody knows anything," was the headline in a report by Yedioth Ahronoth, adding that officials were still struggling to understand whether Trump's remark was serious, two days on.

The Israeli prime minister's office responded to the news several days later, saying that the shift from US aid to partnership showed "the strength and sophistication" of the bilateral relationship.

US military aid is less than 10% of Israel's annual military budget. But Yaakov Katz, author of several books about Israel's defence and security, said Trump's announcement was the tip of a much larger question around future funding, arms sales and joint military projects with Israel. All of this could be slowed or stalled by a Democrat-controlled Congress, even without the two-thirds majority it would need to overrule Trump.

"Everything that Israel used to get in a simpler, easier process will now potentially be much more complicated, and Israel has to be prepared that this is a new reality," he told me.

"Our entire Air Force is American-made military planes, we're dependent on American spare parts and American weapons. The last three years have shown us how dependent we are on American missile-defence systems. [If] those don't show up at the same pace, that's a real difference – that changes your calculation of what you're able to withstand if you go to war." Katz believes the midterms could also translate into tougher demands on Israel over its actions in Gaza and Lebanon, and a requirement not to undermine an agreement with Iran.

"Something will change in the US-Israeli relationship, but it's a question of scale," said the US official I spoke to, who was not authorized to speak on the record. "It means shifting to [being] willing to criticise Israel when it's warranted, but the bedrock fundamental relationship will still be there." In an interview on Israeli television, the US ambassador to Israel Mike Huckabee signalled little shift so far in core American positions, including on Israel's occupation of the West Bank, describing the sanctions imposed by other countries as "irrational" and counterproductive.

Israel's ambassador to the UN, Danny Danon, told another Israeli channel that Trump would be in the White House for the next two years, and that Israel could "feel good" about the US veto in the UN Security Council – something Washington has repeatedly used in the past to block resolutions that target Israel.

"But we have to pay attention to the voices – not only in the Democratic Party but also the Republican Party – criticising Israel," he said. "It will be harder for us." Questions over its key alliance have come at a particularly sensitive time for Israel, less than two weeks after its own parliamentary elections left neither government nor opposition with a clear majority. Discussions are now taking place with the country's president, who will decide whether Netanyahu or his centrist rival, Gadi Eisenkot, will get the first chance to form a governing coalition.

"Under my leadership, we will renew and deepen that [US] partnership, strengthen the bipartisan foundations that have long sustained it," Eisenkot said in a social media post.

Another member of his opposition bloc, Yair Lapid, said: "What do we do?" "We go back to the rule that worked for us for seventy years, and which broke in 2015 when Netanyahu went to speak against [US president] Obama in Congress. Israel doesn't choose sides in America. We work with everyone." Netanyahu's speech to the US Congress in 2015 is seen as a defining moment in Israel's relationship with the US, when the Israeli leader appealed over the head of America's Democratic president to urge Republicans in Congress not to back a nuclear agreement with Iran.

Since then, Netanyahu has increasingly anchored the alliance in Trump's Republican party, even as alienation among Democrats has grown.

The US official I spoke to said that, before the midterms, Netanyahu could have improved the relationship with Washington by getting rid of his two far-right ministers. "I think everyone understands now it's bigger than [that]," he said.

How much the new tone in transatlantic relations will play into the task of building a new government in Israel is being closely watched.

Some government supporters argue it has increased the need for political stability, and that Netanyahu provides much-needed continuity and a deep knowledge of the US and its leaders.

"We cannot afford to be dragged into endless political disputes and election campaigns," said one opinion writer in Israel's largest-circulation daily, the right-wing Israel Hayom.

Whoever heads Israel's next government, its American ally may demand more than rhetoric.

In the noisy debate around what this will mean for Israel, the silence of its prime minister – once the whisperer of Washington's elite – is perhaps the most telling voice of all.