So, we should take the James Taylor approach to international relations.
The US gun culture is due to capitalism.
People with any mental illness should be denied the ability to purchase a firearm. 

In reality, the country with the weaker military has no say and is ultimately invaded and taken over.  The US gun culture is primarily due to the 2nd amendment, adopted after the Revolution, and has evolved from there: that money is made off of gun sales is not the cause, it is the effect of the 2nd amendment.  
 
The gun laws in the US are not lax, their implementation of them, however, is.  States do not co-operate with the Federal level.   Automatic weapons are banned unless you have a specific licence, but a semi-automatic can  be made fully automatic with an easily bought add-on.  

I will agree, however, that "rights" become entitlements, and not privileges with responsibilities.  This is seen increasingly so in N. America, with almost every "right" we are privileged to have.