In your view, do the president and Senate have the power to make treaties that enhance federal power at the expense of the states?
No, as a nation we need a unified voice. The federal government should be charged with making these decisions lest we divide ourselves.
Shouldn't. The constitution says it's the supreme law of the land and it establishes the barrier between state and federal power. I believe scotus, however, has interpreted treaties to trump federal and state law, but I don't know this for sure.
Some constitutional scholars argue that the Tenth Amendment bars certain kinds of treaties.
I'm surprised at that. The tenth has always been considered a "truism" because it doesn't add anything new the constitution; it just clarifies what is already there, meaning the enumerated powers already limit federal authority.
It's not so clear cut. During some time periods, people have called the Tenth Amendment a "truism."