This is true, its already affected a lot of American sport cars ala Mustang, Camaro and Vette. EPA cracked down on several large shops that cater to these platforms and its not ending there. That is why Ford has CARB EO and warrantable power kits available for some of their cars. I have the Ford Racing Power kit on my 2020 Mustang GT and it has an EO# as well as a factory warranty for 3yrs. 36kmiles as long as its installed by a dealer or ASE certified mechanic. 2018-2020 Mustangs are putting down 440rwhp with this kit. BMW should do the same.
The days of catless downpipes and even high flow cats are probably going to be coming to an end as well as tuning. Roush, Livernois and Ford offer smog legal tunes now for owners.
This isn't a state thing, so people will say "my state doesn't smog test." Its an issue of not being able to buy it new anymore as the EPA (Federal) is leveraging huge fines to these vendors for this.
So tuners are going to have to step up and get their stuff EPA or CARB legal. CARB is California but it has the strictest paramaters. So if its CARB legal its legal in all 50 states.
Dave