... the Niger delta supplies 40% of all the crude the United States imports and is the world capital of oil pollution.
That's blatantly wrong, as you can see from the official statistics from the US government here. Nigeria as a whole provides closer to 7-8 percent of all the crude the United States imports. The Niger Delta is entirely within Nigeria, so there is no other country that contributes to the figure for crude from the Niger Delta.
Overall, Nigeria is far behind Canada (in first place) and Mexico (generally in second place) as a crude supplier to the US. Nigeria generally vies for third place with Saudi Arabia and Venezuela.
The unfortunate thing is that when you see such an obvious inaccuracy, you doubt the rest of the article.