While you're waiting for a more detailed answer about Panama specifically, you may be interested in this old post about how continental Latin American states more broadly gained their independence. It only has a line or two about Panama, saying there were pre-existing secessionists, but they weren't successful until the US strongly threw their weight behind them. This only happened when Colombia, which controled Panama before independence, declined to ratify a treaty allowing the Panama Canal. Panama became independent in the early 20th century, but other continental former Spanish colonies became independent eighty or more years earlier.