Did the United States fund Israels Iron Dome defense system ?

Yes. Since 2011, the U.S. has given at least $1.7 billion to the Israeli military for Iron Dome, which includes funding through 2028. This is in addition to the $3.8 billion the U.S. gives the Israeli military each year - far more than any other country - as part of a 10-year memorandum of understanding (MOU) that was agreed upon in 2016 that covers the fiscal years 2019 to 2028.
Israel is the largest recipient of foreign funding in U.S. history and the only country that does not have any country-specific human rights conditions attached to its military funding. Since Israel was established in 1948, the U.S. has given it more than $146 billion in military, economic, and missile defense funding ($236 billion adjusted for inflation in 2018 dollars), the vast majority for Israel’s military. Israel is capable of funding Iron Dome on its own without U.S. taxpayer dollars.