If only part (but crucial part) of high tech weaponry was available could certain tribes defeat US forces?

As we know there are still many tribes in Africa and S.America etc... who try to fight US forces but is the key having access to just a handful of technologies? Lets consider this, radioactive shells are used to break armor on tanks etc... Lets consider if a Zulu warrior had say, radioactive tip arrow heads and titanium shields, given they would be able to M1A2 tank armor and stop all but APC bullets. The arrows would be effective against the soldiers body armor too. I believe such a situation would seriously disadvantage US forces against say a united Zulu affront. Consider how much more powerful this force would be and could you envisage the US defeat? How would you avoid heavy casualties in such a situation?