Unfortunately the problem of "colonizers" and "colonized" described by Fanon still exists in the present day but in a somewhat different guise.
The Wretched of the Earth is anomalous in some sense because at the time it was written in 1961, most of the "decolonization" had already been accomplished (or forced upon the colonizers), except for, primarily, apartheid South Africa. Fanon was nevertheless depicting a situation that exists even when a state is not controlling other countries by force, as had been the case with respect to the British control of India and the overall European control of Asian and African nations. Or, he was not necessarily describing a literally still-existing situation so much as he was prescient that this dysfunctional dynamic between different peoples would not be solved soon. Today, the same problem exists internally, to a large extent, within countries that are "multicultural" in the sense of having different ethnic or racial groups and to which immigration from other countries is occurring that may increase this internal diversity.
In Europe many immigrants have come from previously colonized regions and become citizens of Britain, France, Italy and other countries. Often there is antagonism from the indigenous Europeans and a failure to integrate the previously colonized populations. Right-wing groups have become stronger and have a subtle (or unsubtle) agenda of keeping the immigrants marginalized or (in the most extreme form) even expelling them from Europe.
The U.S. has its own problems along the same lines. The most obvious form of it is the institutionalized racism that persists against African Americans, the equivalent, in U.S. terms, of a colonized people. The additional problem is that demagogic politicians have stirred up majority Americans against immigrants to the U.S. from Latin America and from majority-Muslim states throughout the world. It is a thinly-disguised (or actually not disguised at all) form of racism in which the dynamic of a colonial society is being reenacted, except that in this case the "colonizers" are trying to keep the "colonized" out of the country entirely.