What "gross miscalculations" did the UK/USA make that caused the USSR to "tighten its grip on current possessions"? Communists in China, Yugoslavia, Poland, Hungary, Greece and others were answering to the USSR, because the USSR was funding them.
As to your claim that the US capitalized on "gains" it made in two world wars, I don't know what that means. The Potsdam and Yalta conferences were about an agreement as to when those nations, whose governments were destroyed by war would hold free and open elections - the US lived up to its part of the agreement, it was the USSR that reneged. No country was entitled to territorial gains and no country but Russia kept territories it had liberated from the Nazis. That American "loan" you referred to, was called the Marshall Plan, which was called by Churchill, "the only unsullied act in the history of the world."
Stalin tightened his grip on the Baltic and East European countries, because historically Russia has always used those countries as a buffer and Russia thought that they were entitled to those countries by tradition - that was the "perceived threat", which as it turned out was not just a threat but reality. Has America historically been at odds with Russia? I don't know, but the fact that we purchased Alaska from Russia, instead of helping ourselves, would indicate some level of co-operation, and during WW I and II, we seemed rather supportive of Russia - in 1917, America sent a volunteer group of railroad engineers and workers to the Eastern Russian empire to rebuild the railroad system, which had completely broken down - no goods at all were moving from any Eastern ports. During WW II we actively supplied Russia with raw and finished goods and considering the fact that both oceans were fraught with danger for US ships, I would call that support and after the attack on the US by Japan, the shipments continued even though we were no longer a "neutral" country.
I have no idea as to what "conspiracy" anyone is referring to...