So yet again I ask; how would you go about it? If a spate of school/university/public place shootings isn't enough to persuade to reconsider their stance on firearms ownership (if anything it just made the sentiment stronger in many cases) then what are you suggesting will?
Where is it you think they'll go? Either people will hand them in or they won't, and in a country with firearms as a part of their culture, many won't. Not to mention the already-plentiful number of illegal firearms already in circulation.
So having illegal firearms in circulation isn't considered a problem?
Again, no idea why you keep bringing the UK into this.
You're still looking at this as a ridiculously simplistic thing. How do you even expect such a law to get passed in the first place? Why would America want to do it, and how would they ever get it past the various levels of government? Hell, the NRA has 5 million members and is a powerful lobbyist, you really think they'd just roll over and hand their guns in?
No, it isn't. Unfortunately you're so fixated on your impossible fantasy of a gun-free USA that you refute any criticism made against it without even taking the time to consider the points people are making.