There are of course many ways to kill and someone who is determined to do that is hard to stop, but the ease that assault rifles and hand guns gives to that purpose will always make it the number one choice, and these weapons are the ones that you cannot get away from and make it possible to kill so many in a matter of minutes.You're right, in USA guns are almost 100% responsible for deaths.
I referred to cars or trucks because they were used in Nice France (87 deaths) and in Toronto (10 deaths) and a few others plsces in Europe.
Yes you can drive a car with a bomb in it into a crowd and kill many but that takes an amount of know how and is almost exclusively used by trained terrorists not the usual pissed off lunatic that we keep seeing in the US.
You see it now happening in other countries also but no where near like in the US and the obvious answer is the millions of guns out there, and the ease of being able to obtain it, no other country comes close to the US in that regard.