Are you saying that the main US credit union insures all depositors' FCU accounts? That does not sound right. My deposits are insured by the NCUSIF. According to my credit union, "All deposits are federally insured by the full faith and credit of the US Government to at least $250,000 through the NCUSIF - the National Credit Union Share Insurance Fund."
Maybe different credit unions have different ways to insure doposits.
doposits->deposits