Do constitutional rights apply to non-citizens? I always thought the constitution of the USA was for USA citizens, but then I'm not from the USA and am watching all this from very far away.
Non-citizens don't get the right to bear arms as far as I know.
The Constitution actually takes away our rights. It has to, it lays out the powers the government has over us. Even the bill of rights doesn't technically give us rights---it explicitly details the ways our government cannot operate.
These are natural rights. The constitution, as you say, delineates state powers as a necessary infringement upon those rights.