They didn't shut down the Comintern, their official organization for subverting and destroying us, until 2 years minus about 5 weeks after Operation Barbarossa (the Nazi invasion), while we (the US) started supplying them with equipment on credit ~3 months after (for gold and minerals before, while the first arrangement was hammered out).
They refused to supply us with meteorological info, which seriously hindered our campaign against Japan.
They seized all the B-29s that were forced to land on their territory (was later copied as the Tupolev Tu-4); while this was consistent with their need to maintain their neutrality towards Japan after some engagements in Manchuria (where they owned the Japanese, but they really needed those troops; Georgy Zhukov earned his spurs and vital experience there), holding the crews was not, I think. They were "allowed to escape into American-occupied Iran" per Wikipedia and e.g. Tillman's Whirlwind: The Air War Against Japan, 1942-1945 (http://www.amazon.com/Whirlwind-The-Against-Japan-1942-1945/...).
This of course says absolutely nothing about how the two peoples felt about each other, and our mutual gratitude for what the other did in terminating Nazi Germany with extreme prejudice.
Was your visit during the Cold War?
The Russian families who took us in were some of the warmest, most hospitable people I've ever met. They really worked hard to integrate us as well as they could and give us a memorable experience. In fact almost everywhere we went, even out into the deep countryside, we were treated incredibly well by almost everybody.
We got to return the favor later when their kids came to stay with us, and apparently that particular exchange program continued on for many years after that. I'm almost sad to say I don't think the Americans they met were as universally warm or welcoming.
Watch "Enemy at the Gates" sometime, especially the first part.
When I was in high school, I had the honor of being chosen as a "musical exchange student" along with a dozen other musicians from local schools to spend a summer in and around Yekaterinburg. While there, we formed a small chamber ensemble and played music for various local groups, including several WWII veteran retirement homes (Great Patriotic War Vets). After our performance, many of the very old vets came up and were beyond warm in thanking us for coming and playing for them. A few mentioned remembering the Soviet-American alliance and lamented our animosity since then, they hoped our countries could be friends and we'd have a long future together.
Curious, we visited various GPW memorials and museums and such. It was a pretty intense education. It was the first time I had ever really heard a non-American perspective on the war and the scale of the Soviet involvement, something I had been completely ignorant of before that point, kind of blew my mind. It really set in my mind the importance of not accepting the education I was fed and to expand my horizons to try and look at things from different angles.
It gave me the travel bug and I try and go out of the country at least once a year since then.