Your assertion that the interstate commerce clause is a broad grant of power is simply bogus. It wasn’t. It was not interpreted that way until well after the Constitution was ratified in the 20th century. The Founders intended that the provision be used to free up interstate commerce, not tie it down in Federal bureaucracy, which they did not even foresee existing at all.
Furthermore, even granting that the TSA is constitutional, which it isn’t, its procedures are not matters of Federal law. The Constitution nowhere grants the Feds the right to do what the bill wants to forbid, and specifically it in the 4th amendment (I do not recall giving up my 4th amendment rights because I want to fly cross country), and so the Supremacy Clause does not apply. Furthermore, the TSA scans/frisks people regardless of whether they are flying interstate or simply intrastate.
The Supremacy Clause only applies to the Constitution and laws made pursuant to the Constitution. TSA scans/frisks are not laws made pursuant to the Constitution, nor are they “necessary and proper” to enforcing a law made pursuant to the Constitution. Therefore, the Supremacy Clause does not apply.
The constitution is very general and deliberately so. Did the Founders foresee flight as an important concern of the federal authorities? No, not likely but they provided a framework within which it could be handled. They did have the concept of a mighty empire whose bounds stretched from sea to see. That would be impossible without the constitutional authority to coordinate and regulation fields never considered in 1787. Had they meant to limit the authority to state rules and regulations they would have said so.
Nor will the fourth amendment allow people to fly unsearched. They can retain that right and refuse but they will not be allowed to fly. Airlines have an overriding right to prevent bringing on board of items they want to exclude. Fourth amendment rights have nothing to prevent that.
Your opinion of what is or isn’t constitutional has no bearing or force other than that of opinion and isn’t not based upon anything other than your dislike of the searches.