I have no idea if EU countries track such imports or if they require certification before these imports are allowed. Some states may, some may not.
Keep in mind, MOST (but not all) aftermarket exhausts Made In USA are technically illegal. That is, they are NOT "Type approved" by the EPA or CARB (in California) for your bike. Even though the exhausts are illegal, thousands are sold and shipped out every day.
The EPA (environmental protection agency) have only prosecuted a few key US manufacturers ... mostly those supplying Pipes for Harley's, like Cobra, Vance & Hines and a few others. Warnings have been issued to others ... yet business continues to thrive. How?
They sell them with the designation : OFF ROAD/RACING USE ONLY
Once on the bike, here in USA there is (for now) no real enforcement.
But Europe is a different world. I've no idea how things work regards the importation of aftermarket exhausts. If the manufacturers designate your pipe as 'Racing only" then perhaps it can get through? A dealer could probably import it. Or perhaps they don't even enforce or don't have such restrictions?
But if your country has annual inspections like the MOT in the UK, then they could catch you out ... if they restrict non
standard exhausts. Most US states have no such inspections, some have SMOG checks, but not sure if they flag illegal pipes or not. In California we have no such annual checks for bikes ... YET!
If me, I'd buy a quality Euro made and approved system like from Austrian Remus. Another is Akrapovich. Both, IMHO, better quality than anything Two Brothers make, who are "average" at best.