In order to discuss this sensibly, it's necessary to distinguish the social-democrat left from the actual Communist left. "Fabian" socialism as opposed to revolutionary Marxism. The former pursued economic redistribution, the establishment of public healthcare and education systems, and nationalisation of some industries while generally leaving private property alone and retaining elections. The latter didn't, and were often thoroughly infiltrated by actual Stalinists and KGB agents. Although not as thoroughly as Joe McCarthy would have you believe.
Another key point is that European countries became command economies (or at least heavily requisitioned economies) as soon as the war started. Non-state economic activity became very difficult due to lack of resources and manpower, while a huge state economy was built to produce war materiel and ration everything else.
Let's also not understate how much was destroyed, and how many people were killed, exiled, expropriated, wounded or seriously inconvenienced by the war. It was a war of indiscriminate destruction from the air. A significant fraction of Europe's remaining traditional hereditary aristocracy were killed, in some cases wiping out entire family lines.
The existing social and economic order was simply blown to pieces, a lot needed to be (re)built, and everyone was already mobilised. It's a short step from state-directed building of aircraft, hospitals and barracks to state-directed building of cars, hospitals and houses.
America suffered no such destruction of property, providing less of an opportunity to redistribute its replacement. Meanwhile the foundations for post-war technological industries were being built around the arms manufacturers, and the post-war space race.
There were a lot of public left/right confrontations in various countries in the 60s. Everything from the US civil rights movement to the soixante-huitards to the Greek internal conflict which collapsed into a military dictatorship. Italy could have gone either way (and the CIA were involved there, in Operation Gladio). Also de-colonialisation by France and the UK; arguably this is a shift to the "left".
It's also important to look at how pivotal individual figures were and how differently things could have gone if, say, JFK and MLK hadn't been assasinated. The US could have ended up not so far to the right.
But ultimately a lot of the US "rightism" was straightforward power politics of anti-communism, competing against the Soviet Union. This included sponsoring terrorism and coups in South America, the Vietnam War, and so on.
Edit: this is a huge question, really. How much of "Europe" are you counting? France+Benelux+West Germany+Scandinavia+Italy count as "left", I suppose, but what about military dictatorships in Spain+Portugal+Greece?
About bomb damage in the UK: while this only affected a small fraction of buildings, it was an omnipresent threat in any urban area. The British victory is seen in popular history as fundamentally collective - "pulling together", "blitz spirit", Dunkirk's "little ships", rationing, etc. (Slightly contradicted by talking about "the few" of the air superiority fighters and the aristocratic flavour of the RAF, though).
America lacks universal health care partly because of a persistent popular belieft that ill-health reflects immorality, while the UK set its up at a time (1944) when anyone could be injured by shrapnel at any time without it being a reflection on their character.