Biden's never said whether he took any antihistamines or cough meds. Even bendryl or its generic can knock some people sideways. Taken in sufficient quantity, Robitussen DM can cause hallucinations.
Naturally Biden didn't OD on Robitussen. But most of us did, in college. And we could NOT have appeared on a stage and done anything more--or less--than disgrace ourselves. And of course we all know the potential dangers of mixing meds, even over the counter meds.
Jet lag, you say? It can affect you differently as you age. I once caught a very bad cold while flying from Milan to the States. I ended doing very little except sleep for several weeks. And I was almost 30 years younger than Biden is now.
Guess what? Getting old sucks. But it doesn't necessarily make you an idiot. I'm guessing you're pretty young. You'll eventually come to understand this, if you're lucky enough to live that long.