There isn't anyone that knows much of anything about U5a2b1. Unlike older haplogroups like U5a it isn't popular and therefore hasn't been studied much.
Here's a list of U5a2b1 samples provided by Ian Logan. U5a2b1
They're all from Eastern Europe(Russia, Poland, etc) except for a few. Two are from Italy. U5a2b1 is probably most frequent in Eastern Europe. It's distribution though probably extends to every part of Europe and Asia(xEastern edges of Asia). Besides that pretty much nothing can be said about your haplogroup.
One aspect of the history of your U5a2b1 is well known because it's documented by ancient DNA. U5a2b1, like all U5, derives from Paleolithic Europeans. Something like 50-80% of people across all of Europe in the Mesolithic belonged to U5. U5a was the primary form of U5 in Eastern Europe, U5b was the primary form of U5 in Western and Southwestern Europe(inclu. Italy).
Today U5a peaks in Eastern Europe, NorthWestern Europe, Western Siberia, and the Caucasus mountains at 5-6% across the board. The highest frequency is in the Baltic states at about 10%.