Playing EU region but connected to US region host (IP 173.192.12.52)

I play on EU but connected to US region and having high latency (about 200ms delay).

Google says that IP 173.192.12.52 is USA region.

Please fix this problem.

This is indeed in the Dallas server farm. Did you start a new instance, or was it possibly made by someone who plays on the NA gateway? Even if you were in a group who wasn't in that particular area, someone could have traded something with someone there and kept that instance, or were in it before joining your group etc... If you force created that instance new, or were solo for at least 15 minutes before going there, then there's still the possibility that the EU gateway was full and it needed to create the instance in America for you. If you were in a group, it's more likely that instance was made by someone in the NA gateway. How frequently do you notice joining NA instances?

It seems, it happens only when I play in group.

I see, if you create the instance, they will be connecting to servers in your area, otherwise you'll be connecting to theirs. Control-click the portal or WP mark, and you can see which gateway it's running on.