You can explain it every which way. It's just gonna be acceptable enough for people here who can't relate.
Dominicans, while jovial and fun, are taught to be insular. Your friends are your family and your family are your friends. Dasit. "We all we got" is a thing for Dominicans too.
Historically, outwardly claiming your blackness in Trujillo could get you killed. Literally. That shyt was happening even after he got killed, as recently as the 80s, so claiming ethnicity first is part pride, part defense mechanism. DR in America is still relatively recent compared to other ethnic groups. The first wave of kids who moved to America are still in their 40s/early 50s at best. A whiter Dominican doesn't claim that they're white first in America. A black Dominican doesn't claim they're black first in America. Why? There's an understanding that Black and White people exist in America and they're not us. Not saying that's a bad thing. Just pointing it out. Don't call em Puerto Ricans, Mexicans, Venezuelans, etc. FBA's just happen to be the ones who take it the most personally, but that's because they can't relate to someone claiming ethnicity above all. That fundamental difference is the source of a lot of bullshyt. It's a game of semantics Dominicans can't win no matter what in America, so claim DR and go about your life.
Lastly, there's no incentive to claim race over ethnicity if the plan ain't to stay long term in America. The goal is usually to come to America, make money, convert it to pesos and retire without a care in world back to DR and only come back if you got family that settled here. Unlike Puerto Ricans, becoming American is an option Dominicans don't have to take. If anything, what you get are kids born here who get dual citizenship in DR JUST in case.