OK, my bad ! I often get where you’re coming from
One’s status at an embassy abroad is bit tricky. Although I had more freedom that others and the trust of the Ambassador, I couldn’t go around acting or looking like a homeless person. At least not as a US Soldier.
The Chinese (due to their socio-economic status) are more likely to live among natives & move around natives without arousing too much suspicion. Now if any of the many Chinese I see around Nigeria (all nooks & crannies) are involved in intelligence gathering or in-country studies - then Beijing is likely to have a better understanding of Africa within a generation than any Western power.

There are over 260,000 Nigerians living in America and 10% of those have post graduate degrees. That’s not only a big deal, that’s a strong voice. They are either not supporting you back home, or have no immediate intentions of returning “home”. In comparison, there are but 25,000 Estonians living in America. Also very well educated, but, staunch supporters in Washington.
Nigerians in the US are divided along ethnic & religious lines. 260,000 isn't very significant in a nation of 300 million - especially a nation that has little interest in Africa. In addition, Nigerians don't exactly have a stellar reputation in the US. So I don't see US attitudes towards Nigeria changing in my lifetime.

Yes, most are still stymied by the cultural gap. But, entering those countries for purely political reasons is where most see the underlying problems. French colonial rule in Vietnam was certainly not a demonstration of cultural awareness either.
I don't know much about the French in Indo-China, but I know a lot about the British in Nigeria (and the French must have done something similar in their colonies). Understanding native cultures was the key to a successful colonial enterprise. The Brits governed Nigeria with a few thousand administrators and soldiers, so they had to lean heavily on local administration structures.

For example, in Northern Nigeria, the British used Islamic emirs to administer the empire, collect taxes & administer justice. They made mistakes along the way - and they adjusted. This was very similar to British rule in India through the "Maharajahs".

In South Western Nigeria, the traditional leadership structure was less absolute, women were better represented in the traditional structure - once again, the British adjusted to the peculiarities of that part of Nigeria.

In the South East, traditional rule was more democratic and an attempt by the British to impose "warrant chiefs" & collect taxes led to a riot by market women in 1929 (in Aba). The British had to adjust, and make more use of "district commissioners".

The British & French had scores of "district commissioners" (or their equivalent) who not only spoke the native languages but had a pretty good understanding the lay of the land. The British Army was structured a lot differently from today's US Army - there was the "Colonial/Indian Army" (in which officers spent entire careers in) and the regular British Army.

My point? British & French have institutional knowledge that the US will never/can never have.

I was unable to find any recent statements by Ambassador McCulley. Are we talking about the current Chargé d’Affaires Maria Brewer ? She has been in charge since August 2013 (meaning there is no Ambassador in Abuja).
I didn't know McCulley was no longer ambassador? He was queried over his call for the Nigerian government to establish a "Ministry of Northern Affairs". He was unaware that the term "Northern Nigeria" was pregnant with political symbolism or that it would be difficult to make a case for diversion of Niger Delta resources to solve a problem in Nigeria's North when the Niger Delta is also grappling with its own insurgency.

Added to that is the impression that US was telling Nigeria how to run its internal affairs.

Simply put, a UK High Commissioner is unlikely to be caught making such a gaffe - they understand context better.