I stand corrected.
Could the people there have done anything?.
Maybe. But what. Two crazed men with cleavers, a gun. Rigby was attacked and killed quickly, they attacked men who tried to intervene.
The British people don’t walk around with guns, even those of us who own them. We have little CC in the UK. And even then that’s a small amount of CC in Northern Ireland and a tiny amount on the mainland.
The criticism from the US seems to us to be perfect hindsight. Allied to a bit of BS bravado. Remember the US has its own history of people killed whilst others did nothing.