Immigrant populations in both France and the United States are in the mid-teens, percentage-wise. [1]
Japan's immigrant population stands at 2.0%, and Guatamala's is 0.5%.
I'm aware that there are other measures of diversity, but many of the comments here were mentioning the United States's border with Mexico specifically as a reason for its high murder rate, which doesn't seem to hold up once you dig into the numbers.
I think the other measures of diversity are the ones that are important. For instance, an influx of Canadian immigrants to the U.S. would, I expect, cause no problems at all because Canada is by and large very culturally similar to the U.S.
The border is important in my thinking mainly because corruption and organized crime are endemic to Mexico, though immigration of people from a significantly different ethnicity+culture is also important in the U.S. picture.
Paris, yes. France, no.
France as a whole is very homogenous.