Leaders face a rather difficult situation: the governments of nations exist to protect their own citizens. Were they to export supplies to others, citizens wouldn't be happy. Even were it to save twice as many citizens in a foreign nation as it would have saved in the exporting one. Would you be happy with a national government that placed the lives of foreigners above yours? Even if you would, most people wouldn't be.
This isn't limited to international relations, of course. The federal stockpiles of PPE are nearly depleted [0]. If the virus situation in America worsens, some states will be extremely pissed that the early states got a large chunk of the federal stockpiles, leaving none later on for them. Were the federal government to reserve supplies for states that were affected later, they would face anger from those that are peaking now.
> In a global crisis, selfish actions help nobody.
This is untrue. Keeping supplies does help some people, the ones with whom they are kept. It may hurt others, but it does help people.
I wonder if this is something like a prisoners' dilemma situation. A co-ordinated global response might be the best option, but it would require a sacrifice from each nation. Even if they might benefit in the end, in the days of non-stop media coverage, no government is willing to take the heat for making that sacrifice.
> In a global crisis, selfish actions help nobody.
Officials are elected to serve the need of their own constituants first and foremost, not foreign interests. There is nothing selfish about that. The American government doesn't have to consult with Canada or Mexico before taking a decision in times of crisis. This is the very core idea behind a representative democracy.
Where politicians failed is with their lack of foresight when it comes to stocking masks and ventilators, they didn't fail because they were "selfish" toward other nations.
In a global crisis, selfish actions help nobody.