Here are the two most accurate sites IMHO:
http://www.crimestatistics.org.uk/output/Page1.asp
http://www.disastercenter.com/crime/uscrime.htm
From what I can see crime is stable in the UK and rising slightly in the US. Mugging and burglary are the biggest problems in the UK and murder and rape in the US.
The problem with comparing the UK and US in terms of crime is that although we can easily allow for the difference between a 60m and a 300m population, it is much harder to easily compare countries with vastly different population densities. The UK has on average 246 people per square kilometre compared to 31 in the US, thus it’s a bit like comparing Manhattan figures with Montana ones as we all know population density equals crime! :)
In NYS, where I live, we have something called a duty-to-retreat law on the books. I'd be interesting in seeing what crime rates in states with make-my-day laws have done in comparison to states like mine.
“The UK has on average 246 people per square kilometre compared to 31 in the US, thus it’s a bit like comparing Manhattan figures with Montana ones as we all know population density equals crime! :)”
Those of us who don’t live in the cities understand that very well.