Obtaining a firearm, either by buying one illegally, or making one in a home workshop, is easy and cheap anywhere in the developed world.
The difference between the USA and (for example) the UK is not in the ease of obtaining a gun; It is in the consequences of being caught with one.
In many parts of the US, merely being seen to have a gun is not grounds for police interest or intervention (as long as your skin color checks out). If the cops do care to investigate your weapon, and find that you are not licensed to have it, or that it's stolen property, the penalties are slight. It's a misdemeanour, and a small fine, and confiscation, are the likely penalties.
Being seen with a gun in the UK - even if you are fully licensed and own the weapon in question - will likely provoke a severe police response. If you haven't broken any laws, you will nevertheless be cautioned about causing 'alarm and despondency' (which is illegal), by allowing the public to see it - and potentially be scared by it.
If the UK police find you in possession of a gun that you do NOT have a licence for, then you can expect to be sent to jail for several years. Just for having the gun - you needn't shoot or threaten anyone with it.
The result of this is that criminals don't habitually carry guns in the UK. It's too risky.
Gun control has bugger all to do with making guns hard to obtain. It's all about making guns undesirable to keep, particularly for criminals.
Very few Americans appear to be capable of understanding this simple fact.