Leaders of the BRICS group of developing nations have invited Saudi Arabia, Iran, Ethiopia, Egypt, Argentina and the United Arab Emirates to join, in a move aimed at growing the clout of a bloc that has pledged to champion the "Global South".
When u say US failed to do, you are giving impression that US wanted or tried but failed.
US has severed its relations with Iran since Islamic revolution more than 50 years ago. Its not beneficial for them that Saudi Arabia (their ally) have good relationship with Iran.. Now that relationship between Saudi Arabia and US is getting worse after murder of the journalist khashougji and Biden calling for Bin Salman to be punished, China stepped in and tried get the two countries together