The photo suggested promise. On the sidelines of a peace ceremony in Colombia, President Nicolás Maduro of Venezuela and Secretary of State John Kerry met for the kind of brief exchange that, under normal circumstances, might have been the start of a thaw after years of icy relations.

But these are not normal circumstances: Venezuela’s economic and political crises have left it more isolated than it has been in years — and not just from the United States.

Shortages of food and medicine have left Peru calling for a bloc of countries to pressure Mr. Maduro to accept humanitarian donations, something that he declines to do. Mercosur, the South American trade bloc, has threatened to expel Venezuela over human rights violations and not complying with its trade laws.

And even the State Department, after Mr. Kerry’s meeting with Mr. Maduro, issued a statement indicating that the men’s encounter in Cartagena was not a photo op but rather Mr. Kerry’s chance to express “our concern about the economic and political challenges that have affected millions of Venezuelans.”