I can't talk about England (especially as my english is bad and broken ; ) ) but what are you talking about changing our culture or stuff like that ?
If you are taking muslim only... they are what ? 7% of french population... (after checking, 7,5%) ... what changing can they do ? And you forget something (you must know that already !) French are so stubborn.. we won't change like that !
Ok let's take real number (source are the demography institute ... you can't be more official)
In 2008 (and there isn't a HUGE change since) number of immigrate people(in K) : 11 952 (couting first coming and second generation)
the huge % of that will come from Europe (of course) but i guess that's what you call non-white people... but we really don't have the same culture as the Italian and the spanish (for example)... maybe from your point of view, it's the same "label Europe" but we are more alike with .. I dunno.. Canada, than Spain. But whatever. ok " non white people" things...
for the rest of the % it's equal between asia & coming from " arabic country "
So yeah i can see an influence of both these population coming to us : More good food ! yeah we already have got our own good food... but we like food enough to incorporate foreigner food into our habits (is it ok ?)
You may believe that Marine LePen is a mighty power here... but the "better" result this sh!tty party got is 21% with everyone on the line
France is a country that is really into center.. not too left at all and right side must be "republicaine" (not the same definition of your republican) ... extrem from both side doesn't stand a real chance here (so far)
There is trouble and problem .. based on difference of culture. of course... and based on social drama etc... like in every wealthy country !
but no.. France isn't eaten to the roots by what you call the " non white " population...