The historical reason is simply that the US originated from an oppressed colony. Attempts to restrict guns were one of many ways the king attempted to keep the colonists under control. There is thus, an ingrained suspicion towards attempts to restrict guns. Even if greater availability of guns did lead to more crime, the people of the US felt that some increase in crime was worth the protection from tyranny.
In addition, while you seem to take it as a foregone conclusion that more restrictive gun laws would equal less crime, that is far from a proven fact. You mention the UK, which does have less crime and stricter gun laws than the US, but one data point is hardly proof of anything. Here are the murder rates per 100,000 from Wikipedia:
California: 5.4 (restrictive gun laws)
Canada: 1.7 (restrictive gun laws)
UK: 1.23 (most restrictive gun laws here)
New Hampshire: 0.9 (very few gun laws)
Switzerland: 0.7 (Most males have a military issued rifle in their homes)
My point is not to show that guns make a country safer, rather that there isn't much effect. Crime happens for various reasons, and availability of guns doesn't really affect it.