His disowning of his Nigerian father was plain stupid on his part including the insinuation that the father (who is very wealthy in his own right) is after his money. His mother is not Nigerian. His father has two wives - first English and the second Nigerian. Apart from that, I don't think non-Spurs fans from Nigeria actually care about him again.
As far as I am aware, the clamour for Dele Alli to play for Nigeria wasn't intense. I don't even think there was a concerted campaign as done for Obafemi Martins. At one point, there was a slight interest in him due to him being Nigerian and a central midfield replacement required for Mikel / Okocha. He was on the radar before his move to Spurs. Dele Alli has been to the country severally when he was a kid - we congratulate him on his success and wish him the best. England can and do have him.
We do have a campaign similar to almost any other country (Spain, France, England, Italy) to speak to players of dual nationality to check if they are interested in wearing the GWG. I see nothing wrong with that and find the emotion towards it bizarre. At least we are going for players who have at least one parent who is Nigerian.
Players like Nedum Onuoha, John Fashanu, Gabby Agbonlahor, Patrick Owomoyela are examples of Nigerians who were capped a couple of times by other lands and never played again. There were a lot of Nigerian-English players in that U-20 side that won the WC in 2017 - Sheyi Ojo, Dominic Solanke, Fikayo Tomori, Ovie Ejaria, Ademola Lookman, Josh Onomah.