The problem with the US requiring visas for UK citizens (and many others) goes back to a conference in 1948. Following the Second World War all the nations agreed that free access to each others territories was a good thing.
Every country then signed...apart from the US. From then on British Crews and citizens required visas to enter the US but American Crews coming to the UK and Europe did not. No British Government ever did anything to correct this anomaly or retaliate by insisting on US crew and citizens requiring visas to enter the UK.
I remember a mixed US and Brit crew arriving in Japan. The Brits were allowed in with much courtesy on a bare passport while the Americans were berated and fined for daring to enter without visas. Perhaps the Japanese have the right idea.
Don't blame the immigration guys, they are simply trying to make sense of the political directives. Write instead to your MP or the US Embassy.