I will have to dig for sources, but Egyptian AK 47s made on Russian machinery were imported in the early 80's (they were used in Red Dawn ) followed by Chinese versions. Mosins came in from Finland, and I think Makarov sporting pistols started showing up just before the collapse of the USSR.

But the main source for Warsaw pact pattern arms would have been China, they exported SKS rifles, semi auto AK pattern rifles, T53 Mosin Nagant carbines, TT 33 Tokarev, and perhaps a couple other guns. The 1980s were the heyday for Chinese guns, until import was cut off by executive order.

As /u/mosin91 already touched on, China was/is an important source for Soviet-style weaponry. Not being a collector of Kalashnikov style stuff, or anything Chinese really,, I really am not up on the specifics there, but I do know that there was a rise in restrictions for Chinese imports but Mosin covers it below. What I can talk about is the old school ubiquitous Russian/Soviet arm, the Three Line Rifle, or Mosin Rifle.

The reason that every gun owner that you know probably has a Mosin is the fact that they were built by the million, and after World War II, the guns that the Soviet Union didn't give to its allies or various insurgent groups, were re-arsenaled and backed into crates, to be stored for use in World War III.

The breakup of the Soviet Union meant that all those crates of Mosin rifles that had been stored for Doomsday, and were no longer really needed, could be sold to eager collectors in the West. The market got absolutely flooded, and a nice quality M91/30 could be bought for well under 100 bucks. Prices have risen slightly, but the arsenal refurbs are still available for very cheap. Mosins that aren't part of that 1990s flood can still command a nice premium though, be they Finns, War Trophies, or the coveted US-built Remington Mosin, to name a few examples.

So to segue into the second part of the question, while Mosins could be found on the US market prior to the end of the Cold War, they were somewhat rarer. Imports from Finland, war bring-backs from Vietnam and the like. Additionally, between the passage of the Gun Control Act in 1968 and the Dole Amendment in 1984 which created the C+R exemption, importation of military firearms was almost impossible due to the sporting use clause, and even after the Dole Amendment, that clause complicates the importation of many Soviet-bloc arms (someone who collects Kalashnikovs would have to explain the rules there). The Dole Amendment revitalized the military surplus market, which had been dying for the previous decade, but Communist-bloc weapons were still a rarity until the 1990s.

Ok, I'm back from hunting for telegraph insulators along an abandoned railroad track (failed, construction in the area made the walk too long, so didn't feel like going) and photographing old graves at the local pioneer cemetery (success, I'll be posting the markers of some WWI vets in /r/wwi when I get the energy to upload the pictures.)

Here is an account of the Egyptian Maadi AK 47's used in Red Dawn . These would be some of the first Russian style AK's available in the United States.

Executive Order 12938 signed by President Clinton cut off the importation of arms and ammo from NORINCO due to their proliferation of weapons of mass destruction. Prior to that, President GW Bush had banned the importation of "Non sporting" arms from China, which resulted in the redesigned MAK 90, and the shipping of SKS' without installed bayonets. Until the Clinton ban, China had also been a source of Tokarev style pistols in 9mm and the original 7.62x25mm, as well as

According to this Baltimore Sun article The former Soviet Union had sold 18,000 guns to the US. I haven' been able to pin down what those guns would have been, but it is likely that some were sporting shotguns and such, as well as Makarov pistols, and SKS rifles.