Speaking in front of an unfinished section of border wall, Trump said his Democratic successor's decision to undo his hard-line policies had led to increased illegal immigration and drug smuggling.
"Biden is destroying our country," Trump said.
Trump remains one of the most influential figures in Republican politics and has flirted with running for president again in 2024.
His appearance near Weslaco at the southern tip of Texas, his second public event in recent days, had the trappings of a miniature campaign rally as he revived old grievances from his time in office, including his 2020 loss to Biden and questions about Trump's mental and physical fitness while president.
At least 31 Republicans in the House of Representatives skipped out of work to attend the event and were recognized from the stage by Trump. Texas Governor Gregg Abbott, a fellow Republican and possible 2024 presidential candidate, accompanied Trump on the visit.
Trump has struggled to maintain a high profile following his loss to Biden in November and after being permanently banned from Twitter (TWTR.N) and suspended for two years by Facebook for making false claims of election fraud.
An accelerating criminal investigation into his business empire could complicate any return to campaigning. The Wall Street Journal reported on Wednesday that the Manhattan district attorney is expected to charge his company and its chief financial officer with tax-related crimes on Thursday. Trump did not respond to reporters' questions about the investigation. read more
Trump's comments on Wednesday come as arrests at the southwest border have risen to the highest monthly levels in two decades since Biden took office, according to preliminary figures first reported by Reuters. read more
Since he took office in January, Biden has reversed many of Trump's restrictive immigration policies. He halted construction of Trump's signature border wall and ended a program that forced tens of thousands of migrants to wait in Mexico pending resolution of their U.S. asylum cases.
Republicans have blamed the increased border arrests on more welcoming policies. read more
They have also signaled that immigration will be a focus of the party's campaign to retake control of Congress from Democrats in next year's midterm elections.
Reuters/Ipsos polling suggests their attacks are having little effect. About 10% of 4,420 adults ranked immigration as the nation’s top priority in a June 11-17 poll, down 5 points from a similar survey in April. Among Republicans, 19% listed immigration as a top priority, down 10 points from April.
Americans' approval of Biden’s handling of border issues is nearly unchanged over the past few months, with 47% saying they disapproved of his leadership on immigration, while 40% said they approved.
Vice President Kamala Harris, whom Biden has tasked with addressing the root causes of migration from Central America - poverty, crime, corruption, and the effects of climate change - urged officials to focus on practical solutions during her visit to the U.S.-Mexico border on Friday. read more
Democrats called on Republicans in Congress to work with them to overhaul the nation's immigration laws.
"Anything less is political theater," Democratic National Committee spokesperson Ammar Moussa said in a statement. Reporting by Julia Harte in Weslaco, Texas, and Ted Hesson in Washington; additional reporting by Chris Kahn; writing by Andy Sullivan; editing by Scott Malone, Howard Goller, Jonathan Oatis and Sonya Hepinstall