Actually, Coulter was right. But for a specific year - 2002, to be specific.
The murder rate in Belgium in 2002 was higher, because there were 318 murders there, (compare to 215 in 2000).
Due to that jump, the average murder rate in Belgium was ~2.2 per 100,000 in 2000 and 3.1 in 2002.
US data for 2002 was: 6,200 white murder offenders (src), total whites 194,822,000 (src), so average per 100,000 was 3.1 as well. Same rate as Belgium.
See my below original answer for 2011 figures.
methodMan's answer uses BJS statistics. However, using FBI's statistics, the numbers are significantly different, as is the conclusion.
Total murder offenders: 14,548, of them 4,729 white. Total white population in USA is ~225mil as of 2010 census (src).
Total white firearm murder offenders: this is hard, since no table exists for offenders by race by firearms. But pretty much ALL tables showing murder weapons (e.g. Table 7) have firearm murder rate around 66-70%, so we can reasonably approximate as 3121 white murder offenders via firearms (4,729 * 0.66).
This amounts to 3121/2250 = 1.39 per 100,000 population - white-offender firearms murder rate, and 4,729/2250 = 2.1 per 100,000 population - white-offender total murder rate.
Those are way lower than "whites only" BJS figures stated by methodMan.
The murder rate total (2.1) is 25% higher than cited 1.7 in Belgium; however the firearm murder rate (1.4) is three times higher than that of Belgium.