One of Obamas first actions as President was to write a check to Hamas for 900 million dollars,now you know who financed the building of the tunnels
The USA can’t do that with Hamas, as they are listed officially as a foreign terrorist organization. What you’re referring to is humanitarian aid that goes through agencies, like UNRWA for example.
And humanitarian aid is something that Israel lets through and into Gaza (Israel has a blockade around Gaza) and thus Israel has no problem with that.
Just a day or so ago, the Israeli Ambassador was speaking at the UN Human Rights Council and he said that Israel has no fight with the Palestinian civilians in Gaza, but only with Hamas.
Also, see Post #5 for what the USA does with money coming in to Hamas from other countries.