I don't know how much clearer I can make it, but here goes.
There are 16 countable parts in your PMKMS, no more than 10 of which can be imported.
You are going to use a US made receiver, so now you need at least 5 more US made parts.
Changing the FCG will give you 3 more US parts (hammer, trigger, disconnecter) now you need 2 more.
The easiest would be the PG and muzzle device
If you you want to keep the original PG or MD, you will need to change the gas piston or add some US mag parts.
The problem with that being, that you would need the US parts in every mag you own.