The CZ75 was a Communist Bloc product, which was not readily available in the US and whose intellectual property rights were not much respected over here. This created an opportunity for a Western European company (Tanfoglio) to produce a copy for sale in the lucrative Western markets. By the time the politics thawed out, the clones were as well established over here as the original.
In the case of the 1911, its patents should have run out during the Depression. I don't know when the copies started, but I'm familiar with some from the 60s.