So a UNODC (United Nations Office on Drugs and Crime) says the murder rate in Luxembourg is 2.5 / 100 000 and 4.2 / 100 000 for the US, means that the murder rate is approx 1.5 times higher in the US than in Luxembourg.
Whilst a US government report may break them down into race etc... The overall rate per 100 000 population such as used by the UNODC is easy to work it.
And in general the murder rate in countries with more restrictive gun laws is lower.
You can't just pick and choose which stats you use, using the overall figure eliminates things such as ethnic background.