Is it easy to buy a gun in many parts in the US?
Depends on what you mean by "easy".
there are many legitimate gunpart shops in the USA. It is as easy as an internet search. you must meet a criteria for buying gun parts even if you may sound as a shcool kid that wants to commit the next school shooting you may also be a legitimate law abiding citizen. Most people with the age to own a gun know the answer to this question.