Really??
I have a very limited understanding of Dharmic cosmology, but I always got the impression that Karma referred to causality that is not perceptible due to its emergent nature... as in, outwardly it may appear that an act and an effect are unrelated yet they are, however a very simple causality (such as the hangover example) may not be wholesome enough to be conceived of as Karmic (it is partially so of course, as with every other action, yet its Karmic "ripple" extends beyond the hangover, or the person in question, or even the planet.
As such (and thanks ebola for reminding me of this!), EVERY reaction has, to some degree, contributed to setting the conditions to EVERY action, itself leading to yet another reaction "ripple". As such, Karma is one of the best examples of an emergent causality.
This, of course, refers to the dharmic concept of Karma/Kama, not the English one which appears differ with causality only insofar as it being embued with a universalist-overtone.
I don't disagree with anything you said. Every event, or act (whether physical, verbal, or mental), has an effect which is infinite. The ripple is infinite and does not stop at any definite point - there is no simple cause -> effect relationship such as drinking -> hangover. I think the ripple metaphor is a great one, because if you imagine the universe to be like the ocean, where actions are like disturbances which affect currents, waves, and even tiny ripples on the surface - those disturbances are themselves actions which affect their environment, and their effects are perpetual ones in a constant flux kind of way. Whether you choose to isolate a single ripple, or wave, is just that - a matter of choice, or even simply the nature of perception and the mind to isolate, separate, and categorize - but there is no ripple which comes into being, exists, and then disappears, just constant flux.
Thus, with the drinking example, yes there is a lot more going on. However: when it comes down to practical matters and conventional reality, certain simplifications can and should be made, otherwise there couldn't be progress on a spiritual path. For example, Buddhist vows include abstaining from killing others, and the reason is because of the accrual of negative karma, which is of detriment to one's welfare. This does not mean that killing is universally bad, or inherently bad (one can imagine situations in which not killing someone would be of greater harm than not killing them). But, as a rule of thumb it is a good idea not to kill people. Ultimately, it comes down to the present moment, and the best possible choice a person can make in the present moment, and the criteria for what the best possible choice is include intuition and reason and learning from the past.
Karma is not a real thing. Buddhist wisdom says that ultimately, all things are empty of inherent existence. Karma is more of a model of cause and effect as it relates to sentient beings. Buddha used the analogy of money, debt, and investment. Negative karmic actions cause a sort of karmic debt which eventually will have to be paid for, and positive karmic actions are like an investment which will bring well-being in some form.
I think of lot misinformed people see karma as a mysterious force of morality which punishes people for being bad and rewards people for being good. In actuality, it is just the empirical nature of reality in which every action has consequences with regard to suffering and happiness. I will say, the issue becomes clearer when you believe in enlightenment/nirvana, which is like the end goal of the game of karma. Without the concept of enlightenment, it just seems like a never-ending game of pain and pleasure - very nihilistic.