> The last time there was a major famine in England, for example, was in the 1650's.

That's an interesting way to cherry-pick a statistic and ignore a genocide (I'll give you a hint: 1840's).

If Ireland had closed her ports, I wonder how much England would have felt the tighter food supply.

England would probably have been fine, considering they were mostly getting inefficient calories like beef butter, milk, and beef from Ireland. Although your citation of the outflows of food is actually a great way to prove my point. There was plenty of food to feed everyone even in the darkest of days, with farming techniques far less efficient than the ones we have now. But shitty economic policy (too small plots of land for tenant farmers, the whole landlord tenant system, colonialism, etc.) and failure to subsidize food consumption for the poor led to really terrible outcomes. Yet there was plenty of food production even when there were no subsidies.

The argument goes that starvation is usually a logistics/corruption problem as much as anything. Technically you can consider the math of supply without it, but practically it matters more than most other things.

Is the current situation unusual, or is it SNAFU?

The Great Irish Famine was systemic problem, not a logistics nor corruption problem.

what is a systemic problem that is not a logistic or corruption problem

That’s the point.

Although the English had all sorts of high minded idealism about the potential for creating dependency amounts the Irish, they supervised the genocide in Ireland.