This is incorrect. Changing your IMEI it is illegal in the USA under the Wireless Telephone Protection Act of 1998:
"Amends the Federal criminal code to prohibit knowingly using, producing, trafficking in, having control or custody of, or possessing hardware or software knowing that it has been configured to insert or modify telecommunication identifying information associated with or contained in a telecommunications instrument"
There are lots and lots of laws, though, that are either unenforceable because they're badly written or just not enforced. The sibling comment pointing out the part you left out is on point, and I would be surprised if any sort of prosecution would ever happen. I'm paying my phone bill and I want to change my IMEI, so what? I'm not defrauding anyone. I am inclined to believe two things:
1) Nobody would ever bother me about this, and
2) Courts would agree with me if push came to shove
Thanks for finding this, as non-US trying to find relevant laws in the mess of multiple levels of law etc is difficult, i assumed the FCC would regulate this as the telecoms regulátor but it appears not
To be fair you're leaving out the last part of that sentence "... so that such instrument may be used to obtain telecommunications service without authorization."
Authorization by whom? I think if I'm paying my bill I have the telco's authorization. They're trying to prevent fraud that gets you free phone service here.
This is incorrect. Changing your IMEI it is illegal in the USA under the Wireless Telephone Protection Act of 1998:
"Amends the Federal criminal code to prohibit knowingly using, producing, trafficking in, having control or custody of, or possessing hardware or software knowing that it has been configured to insert or modify telecommunication identifying information associated with or contained in a telecommunications instrument"
https://www.congress.gov/bill/105th-congress/senate-bill/493