Probably not race related. Ever since Brexit/Covid restaurants are understaffed. We regularly go in to empty restaurants and get told they’re fully booked. If it’s a chain place, especially, the staff just don’t care enough to “fit you in”.
See this recent article: https://www.theguardian.com/food/2022/dec/04/staff-shortages...
Britain is not racist per se, it’s xenophobic. For years before Brexit the group that drew the most ire were white Eastern Europeans.
Being African American might even be an asset as there’s a bit of a stigma against white Americans.