Well, the UK wasn't by any means completely destroyed in WW2 and there's a lot of work being done there to upgrade centuries old infrastructure.
Some examples:
1) The Thames Tideway sewer is being constructed to handle the fact that the old London sewers have run out of capacity and routinely flood sewage into the Thames when there are heavy rains. The problem is that unlike modern sewer systems, London's is used for both rainwater and household sewage. And the original system was designed to overflow into the Thames, on the assumption that would ~never happen. But population growth and lots more concreting means it now happens regularly. The Thames Tideway is a massive, very deep underground tunnel that roughly follows the path of the river.
2) The London Underground is the world's oldest underground railway. It is upgraded continuously. The Crossrail upgrade is the largest construction project in Europe (technically Crossrail is not LU, but it's all a part of an integrated somewhat underground network).
3) The UK road network costs less to maintain than is raised via fuel taxes. The roads are effectively a profit centre for the government, in a sense. They are maintained continuously.
4) The UK water pipe network has had leaks at an economically sustainable level for 15 years now (i.e. the cost to find and fix the remaining leaks is higher than the value of the water lost). It does not use lead piping:
http://dwi.defra.gov.uk/consumers/advice-leaflets/lead.pdf
I don't think there's actually any difference in infrastructure age between Europe and America. WW2 is a red herring. A lot of modern infrastructure runs underground and was undamaged or only lightly damaged by bombing, which was in any case, focused on the cities. The biggest impact of WW2 on the London Underground, for example, is that these days they have to do systematic searches for unexploded underground bombs before doing any work.