I believe the point being made was that in the 50s and 60s in the US there was a large domestic market that had almost no foreign competitors (either they were

I believe the point being made was that in the 50s and 60s in the US there was a large domestic market that had almost no foreign competitors (either they were still rebuilding form WW2 rubble or were way behind US tech) and those same foreign markets were mostly open for US exports. In a lot of industries there was probably a good foreign competitor at the top-end, a few low-end foreign companies, but the vast middle of the market was exclusively owned by US companies for at least two decades.