Treaties have an effect similar to a constitutional amendment.
They obviously do not. If they did, you could basically abolish the Constitution with one with only the presidency, a bare majority of the Senate, and the cooperation of a foreign power. An actual Constitutional amendment must meet a much, much higher bar.
Treaties have and do grant the Federal government additional powers. They cannot diminish powers or add something that is taken away.
And non self executing treaties are meaningless they pretty much mean that the US government promised something but it is not compelled to do anything about it and there is no mechanism that would require it to comply.
The US constitution is supreme it takes precedence over anything the legislative branch might legislate and any action the executive branch might take.
Alien tort is also not accepted when interpreting the constitution so you literally cannot interpret the constitution from the point of view of international or foreign laws.
Congress does get extra power when a law is passed as a treaty. Issues that are state business under the 10th Amendment become federal business.
But it’s nothing like a constitutional amendment.