A visit by the US vice-president, Mike Pence, to migrant detention stations along the country’s southern border highlighted the sharp disconnect between Democrats and Republicans on immigration – and the Trump administration’s efforts to spin on conditions in camps deplored by human rights experts and the government’s own watchdog.

Traveling in Texas on Friday, Pence painted a far rosier picture of conditions in the detention centers than lawyers and several Democratic lawmakers have done, criticizing Democrats’ accounts as “harsh rhetoric”.

Pence and eight Republican lawmakers toured two detention facilities in Texas on Friday, starting with a border station in Donna, a vast collection of air-conditioned, interconnected tents built in May to temporarily handle 1,000 migrants and currently holding 800. Many lay on mats on the floor, covered by foil blankets as children watched TV.

With Republican Senator Mike Lee of Utah, and the Homeland Security secretary, Kevin McAleenan, translating into Spanish, two children told Pence they’d walked two and three months to arrive. He responded, “God bless you” in English and “gracias” in Spanish.

“Every family I spoke to said they were being well-cared for,” Pence said. The press was barred from speaking with any of the children or families to confirm Pence’s account.

Later Friday, Pence visited an outdoor portal at the McAllen border station, where 384 single men were being held in cages with no cots. Men in the portal told reporters that they had been detained for 40 days or more, that they were hungry and that they wanted to brush their teeth.

Men stand in a US border detention center in McAllen, Texas, 12 July 2019, as Mike Pence visited. Photograph: Josh Dawsey/AP

“I was not surprised by what I saw,” Pence said. “I knew we’d see a system that was overwhelmed. This is tough stuff.”

Michael Banks, the border patrol agent in charge of the facility, said that the station was cleaned three times a day and air-conditioned – statements that the accompanying press corps questioned, given the sweltering heat and lack of cleanliness they witnessed.

Earlier on Friday, a hearing of the House oversight and reform committee hearing offered a microcosm of the nation’s red-blue chasm and, perhaps, a chance for each side to vent.

The hearing came as the number of families, children and other migrants entering the US from Mexico has surged above 100,000 monthly since March, overwhelming federal agencies. It also came days before Trump-ordered nationwide raids targeting people in the US illegally are expected to begin, according to administration officials and immigrant activists, actions that would further inflame the issue.

Before Friday’s session began, the panel chairman Democrat Elijah Cummings of Maryland, released a report providing new details on 2,648 of the children the Trump administration separated from their families last year before abandoning that policy under widespread pressure. Unknown numbers of others were also separated.

The report, using data the panel demanded from federal agencies, found that 18 children under age 2, half who were just months old, were kept from their parents up to half a year. Hundreds were held longer than previously revealed, including 25 kept over a year, and at least 30 remain apart from their parents.

The figures reflect “a deliberate, unnecessary and cruel choice by President Trump and his administration”, the report said.

Congress approved $4.6bn last month to help improve conditions. But that measure angered liberals who felt it lacked requirements forcing better treatment of migrants, prompting internal frictions that have yet to fully play out.

New York congresswoman Alexandria Ocasio-Cortez, the 29-year-old progressive icon, was among the four Democrats who testified. After being sworn in at her request, she described migrant women telling her they had to sleep on the concrete floor and drink from the toilet because their cell’s sink was broken.

“I believe these women,” she said. “What was worst about this was the fact that there were American flags hanging all over these facilities, that children were being separated from their parents in front of the American flag,” she said.

The Democratic congresswoman Rashida Tlaib of Michigan was near tears as she displayed a picture she said was of a 7-year-old Guatemalan girl the same age as her son who died in US custody. She criticized harsh policies “intentionally and cruelly created by a Trump administration dead set on sending a hate-filled message that those seeking refuge are not welcome in America”.

Tlaib added, “It’s a dangerous ideology that rules our nation right now.”

Departing the White House, Trump told reporters without evidence that Ocasio-Cortez’ account of women being told to drink from a toilet was “a phony story she made it up”.

Rashida Tlaib, center, wipes her eyes after testifying before the House oversight committee hearing on family separation and detention centers. Photograph: Pablo Martínez Monsiváis/AP

Four border state Republicans sat at the same rectangular witness table as their Democratic counterparts and blamed Democrats for migrants’ problems.

Republican congressman Chip Roy of Texas mocked Democrats’ border trip, accusing them of posing “next to an empty parking lot while making up hyperbole for clips, Twitter followers and cynical politics”. Ocasio-Cortez has 4.7 million Twitter followers.

Roy said by not toughening immigration laws, Democrats have “created the very magnet” that attracts migrants to the US and said the House “cowardly sits in the corner, doing nothing” to address the problems that result.

Last week a report by the Department of Homeland Security’s inspector general found children at some Texas border facilities who faced clothing shortages and lacked hot meals, while some adults were held for a week in a cell so crowded they had to stand.