I am not american either, so what? you completely disregard that any handgun, including these mythical "assault rifles" (which is stupid term by definition, it's usage which defines purpose, so why there aren't any assault pistols?) is just a tool, needing a trained hand to be used. as described below, automatic weapons are not purchasable for civilians, only their modified versions that allow single shot per trigger pull, thus making them effectively small caliber hunting rifles. If you need those, only with special hard-to-get permits, or you need to join the army (and kill few poor people for free)
if you want to stop some crazy people killing with these "assault guns" (why not called home defense guns?), you should focus on removing given dangerous individual from society, and not trying remove their access to weapons. Anything can be used to kill, including scissors, saw, pipe, baseball, knife or just good old pure hands. with current logic, all these things should get outlawed too.
No statistics in hand, but I am damn sure the amount of people killed by legally purchased "assault rifles" compared to say hit & run with cars is neglible. with similar logic I say ban cars! (and it would do so much good in other ways...)
P.S. one last thing - pro-gun-ban people completely disregard gun shooting as a means for hunting and as a fun activity at range. Many weapons, including mentioned AR-15 (civilian version of popular M16) will never be shot outside shooting range. Why use higher caliber guns instead of some puny .22? Because it's more fun!
Ah wait, we're talking maybe to same people that banned almost harmless marihuana and happily kept tobacco and alcohol roaming free on markets...
DISCLAIMER: I never owned any handgun that would require any form of registration, yet before having strong statements about what should/shouldn't be banned, I at least educate myself. Gun ban laws are, apart for some corner cases, just pure crowd idiocy and hypocrisy.