"Blowback" may be a very real danger in international relations, but don't hold your breath waiting for opponents to take revenge or think you can rest easy if nothing happens the next day. Consider the lesson Alexander taught the Persians. When Xerxes invaded Greece in the 5th century BC, he occupied Athens and burned the Parthenon. When Alexander overthrew the Persian empire 150 years later, he burned the capital, Parsa (known in the West as Persepolis), to the ground. The Greeks waited a long time to get revenge.
The Persians in Greece conducted themselves according to a certain standard of behavior; when the Greeks got their turn, they saw no reason to adopt a higher standard. In the event, their behavior was worse - destroying not just a symbolic building but the whole capital city. Such is the way with standards of international behavior - decline is much easier than progress. International standards that take centuries to ga in acceptance can be tossed aside in a moment, after which they are very hard to restore. Once a standard is lost, everyone suffers the consequences. Over the long run, the loss of a standard of international behavior can be far more important than the specific actions that provoked some agrieved party to "violate international law."
Revenge is a simple form of blowback. It has serious implications for national security but at least, if one stops to think about one's behavior, it is easy to predict that when an opponent is eggregiously mistreated, the opponent will contemplate revenge.
Another form of blowback is much more difficult to anticipate: taking an action that sets in motion a fundamentally new dynamic. The more complex (connected, interdependent, co-evolving) human society becomes, the more opportunities there will be for provoking the emergence of an unanticipated political process. This explains why even though human society appears to be getting better and better organized, we nevertheless repeatedly get caught by surprise. We have better communications, trade, transportation, economic links; our cities look increasingly impressive; the world appears ever more solidly under human control; we become increasingly convinced that scientific socialism or capitalism or a "thousand points of light" or democracy will inevitably become the way of the future. Then, the 1000-year-Reich or the Iron Curtain suddenly collapses; the "end of history" comes and goes; empires crash; superpowers discover their feet of clay; rational man bows to fundamentalism. The world is knocked off on a tangent by a shock that comes "out of the blue."
Our behavior will have consequences. The more complex our society, the more surprising these consequences may be. The consequences may come quickly or very slowly, in a form recognizably connected to the original behavior or in what appears to be an utterly unrelated form. We have the power to buy vastly more "foreign policy products" than ever before, but the rising complexity of human society means that we have far less ability to determine the price of those products. Go ahead! Go on a shopping spree! Buy a regime change, buy a scarce resource, buy a country, buy an empire! But you won't know the price until later, and you can't change your mind: buy whatever you want, but you must pay the price, no matter how high it may be.