The highest figure for European origin yDna lines among African Americans I've ever seen is about 28%, with about 6-8% carrying European origin mtDna.
J.M. Lind et al, "Elevated male European and female African contributions to the genomes of African American individuals
Hum.Genet. 120 (2007), pp. 713-72 Abstract.
"The differential relative contribution of males and females from Africa and Europe to individual African American genomes is relevant to mapping genes utilizing admixture analysis. The assessment of ancestral population contributions to the four types of genomic DNA (autosomes, X and Y chromosomes, and mitochondrial) with their differing modes of inheritance is most easily addressed in males. A thorough evaluation of 93 African American males for 2,018 autosomal single nucleotide polymorphic (SNP) markers, 121 X chromosome SNPs, 10 Y chromosome haplogroups specified by SNPs, and six haplogroup defining mtDNA SNPs is presented. A distinct lack of correlation observed between the X chromosome and the autosomal admixture fractions supports separate treatment of these chromosomes in admixture-based gene mapping applications.
The European genetic contributions were highest (and African lowest) for the Y chromosome (28.46%), followed by the autosomes (19.99%), then the X chromosome (12.11%), and the mtDNA (8.51%). The relative order of admixture fractions in the genomic compartments validates previous studies that suggested sex-biased gene flow with elevated European male and African female contributions. There is a threefold higher European male contribution compared with European females (Y chromosome vs. mtDNA) to the genomes of African American individuals meaning that admixture-based gene discovery will have the most power for the autosomes and will be more limited for X chromosome analysis. © Springer-Verlag 2006."
The study can be downloaded at researchgate. Samples were taken from four disparate American locations.
Sims et al found the exact same percentage (28%) for the non-E and non A/B yDna lines.
https://www.researchgate.net/profile...c5fd000000.pdf
There's a graphic of the breakdown.
Sims et al Y dna break down of African American men.jpg
This is obviously different from the situation in Latin America, where the majority of the y lineages are indeed West Eurasian, but that's because until recently most migration to the New World in those places was mostly male. Every situation is different and has its own dynamics.
Oh, the European female lines are estimated to have entered the gene pool during the early days when the African people were still treated more or less as indentured servants, and the best research on the subject I've seen speculates it involved female European indentured servants around the Virginia area where the first slaves were used.