RIO DE JANEIRO — During a whirlwind trip to four Latin American countries this week, Vice President Mike Pence sought to soften the edges of the ‘America first’ worldview — the administration’s first major effort to mend fences with a region rattled by President Trump’s election.

“Under President Donald Trump, the United States will always put the security and prosperity of America first,” Mr. Pence said Wednesday in Chile during the third leg of a trip that began in Colombia and included stops in Argentina and Panama. “But as I hope my presence today demonstrates, ‘America first’ does not mean America alone.”

Yet Mr. Pence’s hopeful message of expanded economic and diplomatic cooperation did little to assuage fears among the region’s leaders, who have been furiously planning for an era of diminishing returns in Washington by deepening regional trade relations and pursuing expanded commercial ties with Europe and China.

Mr. Trump is widely loathed in Latin America, where his early moves have been interpreted as a return to an overbearing, security-obsessed American foreign policy. The contrast has been sharp with President Barack Obama’s administration, when Latin Americans felt they were treated with an unusual degree of deference and respect.