>that sentence makes it seems like Congress could do anything!

Yeah, it's the perhaps most powerful clause in the constitution. A large number of laws are formed like "[actual law ...] in commerce." That is the hook needed for a lot of laws to be constitutional. Technically those laws only apply to interstate or international commerce.

There are even supreme court cases discussing this:

>Congress uses different modifiers to the word “commerce” in the design and enactment of its statutes. The phrase “affecting commerce” indicates Congress’ intent to regulate to the outer limits of its authority under the Commerce Clause. [...] Considering the usual meaning of the word “involving,” and the pro-arbitration purposes of the FAA, Allied-Bruce held the “word ‘involving,’ like ‘affecting,’ signals an intent to exercise Congress’ commerce power to the full.” Ibid. Unlike those phrases, however, the general words “in commerce” and the specific phrase “engaged in commerce” are understood to have a more limited reach. In Allied-Bruce itself the Court said the words “in commerce” are “oftenfound words of art” [...] The Court’s reluctance to accept contentions that Congress used the words “in commerce” or “engaged in commerce” to regulate to the full extent of its commerce power rests on sound foundation, as it affords objective and consistent significance to the meaning of the words Congress uses when it defines the reach of a statute.[0]

[0] Circuit City Stores, Inc. v. Adams, 532 U.S. 105 (2001) https://supreme.justia.com/cases/federal/us/532/105/case.pdf