Do you mean American troops? If so, there are absolutely no American troops in Israel. America and Israel have weapons trading agreements and lots of foreign aid agreements and so a lot of the equipment and/or money for equipment that Israelis use is from the US, but that's it. In Israel it is mandatory for all citizens to serve in the military if they are able. They form the Israel Defense Forces (IDF), which are the army, navy, and air force. The IDF is widely considered to be one of the most professional and well-trained militaries on the planet, pretty much because of the fact that Israel has had a major war on average of every 7 years since the country was founded in 1948, and is constantly involved in small military operations. Because of this, Israel has never had any foreign troops in the country to assist them with military or security needs. The only foreign troops that have been in Israel were the ones that were attacking. If there is ever a war that Israel deems unwinnable, they may ask for direct US or other foreign military assistance, but that depends on the political atmosphere of the time.
While the US offers an incredible amount of foreign aid to Israel, American foreign policy is weary of giving too much overt assistance, like troops. For example, after the US assisted Israel in the Yom Kippur War in 1973 with Operation Nickel Grass (an airlift delivery of much-needed weapons), the response from the Arab world was to economically attack the US with a complete oil embargo, creating the 1973 oil crisis. Because few countries share the same political views on Israel, it is a very delicate political game for any nation that gets involved.
I lived in Israel and I study this stuff. I involved no political opinions in my answer.