In the UK, a weapons amnesty, combined with a threat of severe punishment after the deadline, took most of the unlicensed guns out of circulation and many licensed guns too. [...]
I realise that it will be more difficult in the USA, but if it isn't at least tried, the end result will be a nation of frightened citizens, afraid to leave their fortified (with the very weapons they are scared of) homes.

A national legislated solution obviously isn't going to happen in the US. Ever.

It might not be obviously legal to do anything more local either, but a more realistic approach would be for local communities sick of guns and their pervert owners to tell them to get out. If it caught on, that would progressively leave the gun fetishists confined to their own "free" enclaves until they killed each other off in paroxysms of indiscriminate fear.

The US is great at sloganizing about local democracy and then making sure it never makes any difference to anything, so that's not a whole lot easier, but surely worth trying, despite shit like that recent University of Colorado decision.