You may be thinking about the Palestinian Authority, which does receive money and help from the USA. And that is done with Prime Minister Benjamin Netanyahu lobbying Congress in order to keep the money going to the PA. Israel actually wants that.
But Hamas is not getting money from the USA or weapons. Besides that Israel has a blockade around Gaza and any country who shipped weapons in would be blocked. Hamas has to smuggle whatever they have ... in through their tunnels. It’s not coming from the USA.
There was even an article a couple of days ago where the USA block a money transfer from Qatar to Hamas, so the USA is actively blocking this from happening.
Hamas is a partner in the Palestinian government. The Palestinian government gets massive amounts of funding from the US. Therefore Hamas receives US government funding. Salaries of Hamas functionaries are paid by the US government-funded Palestinian Authority.
The Palestinian Authority, which receives US funds, even pays saleries of Hamas terrorists who are in Israeli prisons. It also pays death benefits to the families of dead Hamas suicide bombers and other terrorists.