BROWNSVILLE, Texas — Damaris Constantino, born on the southern border, is feeling that she is more likely these days to be stopped by authorities and made to prove she belongs in the United States. In contrast, Martín Sepulveda and Dwight Yoder are glad to see a strong Border Patrol presence in their city. They all think children should not be separated from their families.

The seam between Texas and Mexico has created a fabric of American life filled with a citizenry who converse in a mix of Spanish and English and who may quench their thirst with a "michelada" while satiating their hunger with a sirloin steak. Their lives, family and work extend across the international line.

But the Trump administration’s recent policy that separated children from their parents and the ramped-up prosecutions of people entering the country illegally, as well as the push to build a border wall, have some feeling that the symbiotic life they’ve lived here is threatened.

Constantino, 34, was one of a few hundred people who took part in a protest last week outside the federal courthouse in Brownsville, which is in Texas' southernmost tip and just across the Rio Grande from Matamoros, Mexico. Born in Los Fresnos, Texas, about 17 miles north, Constantino's family went back to Mexico when she was 4 and then returned later.

Damaris Constantino, 34, born in Los Fresnos, Texas, joined a few hundred others on June 28, 2018 in front of the federal court in Brownsville to protest the Trump administration's sepration of children at the border and zero-tolerance policy. Suzanne Gamboa / NBC News

Like others who live in Texas’ Rio Grande Valley, Constantino is accustomed to the presence of Border Patrol and Immigration and Customs Enforcement (ICE) as part of the community and part of the local economy. Los Fresnos is where the Port Isabel Detention Center is, which is operated by ICE and where many of the parents who were separated from their children and prosecuted on charges of crossing the border illegally are being held.

Constantino told NBC News she feels immigration authorities' presence in the Rio Grande Valley has become more aggressive.

“We are all brown and we can be their targets. Now we actually have to prove who we are and if we have papers or not, and in the past, it wasn't like that," said Constantino, who held a sign at the protest that read "Love thy Immigrant Neighbor."

“Now it feels like they are taking any opportunity to arrest anyone," she said. "It’s like now, we don’t feel comfortable about them. Their strategy changed."

When your friends are the immigration enforcers

Isis Avalos, 32, said she didn’t realize how unique the Rio Grande Valley border area is until she left for Los Angeles.

Originally from Mexico, she lived undocumented in the U.S. She said she grew up seeing young people cross the border to attend school or to go to Mexico to get cheaper medical care.

“Our border culture is always going back and forth,” said Avalos. “A lot of us have family just on the other side of the river, so we visit our families every weekend or we go out to eat."

"It’s a symbiotic relationship we’ve had with each other,” she said.