WWII: USSR develops nuclear weapons before the USA.

What would have happened if the USSR would have been the ones the develop the atomic bomb before the USA. I'll let your creative minds come up with an answer.
 
Like so many PoD this one needs the details of when and how in order to discuss in any usefull fashion. A USSR that fields a atomic device in late 1944 while the US still progresses the Manhattan project as OTL is a very different situation than a Red bomb deployed in 1946 & the US has no development project.
 
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