I thought about that as well. Suppose a Mexican cartel captured a Russian tourist or diplomat, and beheaded him. Does that give Russia the right to hit targets in Mexico, and perhaps in the US if any cartel members fled here?
If anyone even thought about such a thing, the U.S. would be up in arms, livid at the prospect that a country could suggest violating our sovereign airspace and international boundary.
What's good for the goose is good for the gander.