So, long story short, I constantly get 2k-5k ms in wow on US region. When I switched to EU, 73ms.
Internet speed is not a problem (250mb/s), and on US region my usual ms is 150-190. Clearly the issue is not on my side as I tried all kind of things to fix this issue. Restarts, reconnections, etc etc.
It sounds like you are connecting from EU, but where from and what isp? You can temporarily try a vpn to see if a routing change helps, but unfortunately you will want to work with your isp to check if they are investigating any peering issues.