U.S. graphite supplies—and, therefore, the development of the solar battery—are at risk.
The local chamber of commerce could be an ally here. Many graphite mine owners are members. A strike that stops production is bad for business. So is trying to replace and train a whole new workforce at once. This would cause delays and supply chain problems.
Other allies agree with you that firing union members for striking is contrary to international standards. You could enlist these allies to send a formal request, or démarche, to Myca’s government advising them against taking that step. You suspect that many Mycans will assume that you only care about the graphite, which is not true. You could deliver a speech to Mycan press outlets laying out the U.S. position, which is pro-trade, pro-democracy, and focused on humanitarian aid.