This is true if all studies are equal.
But some studies are peer reviewed and required to cite verifiable sources. Some studies are put out by organizations which are have a vested interest in one outcome or an other.
The later group includes plenty of studies which go in both directions. But the former group overwhelmingly shows that laxer gun control policy leads to a proliferation of guns and this in turn leads to more deaths by firearms.
Show me the data that says that removing the top 10 cities puts the US homicide rate or the homicide by firearms rate comparable to other nations. I will take the time to read those studies and, if they're well designed, I'll update my opinion based on that data.
That is exactly how I changed my position from being against gun control to being in favor of it and if new evidence suggest that this was a mistake I'll change my position again.