The mullahs in Tehran probably slept easily Wednesday, with the satisfaction that they have won this round. That’s because on Wednesday, the US announced that it is pulling its troops out of Syria.“We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency,” US President Donald Trump tweeted.But fighting ISIS is not really the only reason the US has been in Syria. An American presence in Syria made a statement to the whole region that the US is here in the Middle East, engaged and involved.Trump often talks about putting “America first.” Leaving aside the antisemitic history of that phrase, Trump means putting the priorities of his country before all others. There are reasons to stay in Syria that fit with Trump’s way of looking at international relations.A letter written by a bipartisan group consisting of US senators Lindsey Graham, Joni Ernst, Tom Cotton, Jeanne Shaheen, Angus King and Marco Rubio – who dispute Trump’s claim that ISIS has been defeated – says that withdrawing forces from Syria “threatens the safety and security of the United States.”“Both Iran and Russia have used the Syrian conflict as a stage to magnify their influence in the region,” the senators wrote. “Your administration must not repeat the same mistakes that previous administrations have made and concede to these bad actors... We encourage you to reconsider your proposal to withdraw US forces from Syria to ensure that our nation’s strategic interests are secured.”An American departure leaves a vacuum that will be filled with people who harm American and Israeli interests: Russia and Iran.Iran is not shy about its aspirations to wipe Israel off of the map, nor is it stingy in funding partners who are willing to do their dirty work, from Hamas in Gaza to Hezbollah in Lebanon and beyond. They will now be freer to act as they wish in Syria and try to increase their spheres of influence throughout the Middle East.And while Russia has been relatively cooperative with Israel’s security needs in Syria, it has kept up a strong alliance with Iran and cannot be trusted in the region the way the US, our greatest ally, can. We saw this with the recent spike in tensions, after Syria shot down a Russian plane and Moscow blamed Israel.The US is truly Israel’s greatest ally, but the impact of that alliance has grown weaker in recent years. Trump is the second president in a row who has both shown that Israel can ultimately only rely on itself in the Middle East, and who has decided to pull back from American involvement in the world.The result of an increasingly isolationist American policy can only be bad for Israel. Our alliance with the US is a strategic asset that makes Israel significantly stronger, both in quantifiable military might and in how we look in the eyes of other countries in the region.On the first count, the US has kept up its side with a 10-year commitment to give military aid worth billions of dollars to Israel each year.But Israel has more to worry about on the second count. When the US decides, of its own volition, to make itself a weaker player in the Middle East, Israel is weaker as a result. Israel is stronger with an involved America backing it up. US support is one of the considerations our enemies likely weigh when considering whether to lash out at Israel or not, and while the US hasn’t backed down from its support from Israel – and in many ways has increased that support – it won’t carry as much heft without the US continuing to be engaged in the Middle East and the world.After the American announcement, Prime Minister Benjamin Netanyahu said that Trump had informed him of the decision and “made it clear that they have other ways of expressing their influence in the area.” Netanyahu added that “we will take care to maintain the security of Israel and to defend ourselves in this area.”But that ability took a hit, and Israel will have to work that much harder to keep its citizens and its borders safe. Withdrawing American troops from Syria is a mistake for which the US and Israel may end up paying dearly.