We have to begin with clarity about how the crisis engages U.S. security interests. It's widely understood that seizing Crimea alone has not appreciably increased Russian material power relative to the status quo before political upheaval in Kiev. President Obama said as much in Brussels on March 26 when he noted that a "coldhearted calculus" would mean looking the other way in response to limited Russian expansion. But there are two outcomes American decision-makers likely feared from the outset, each for a couple of reasons.
These two outcomes remain a possibility. First, Russia may attempt to seize more territory as a continuation of the present crisis, either because of perceived Western indifference or, alternatively, because of a strong Western reaction that induces genuine Russian insecurity or provides Putin a pretext. These resemble the classic dangers in Jervis's deterrence and spiral models, respectively.
Second, looking beyond the current crisis in a way that will annoy political scientists, American officials are probably worried that other countries, especially China, may mimic Putin down the line on similar territorial issues. This could happen either because perceived inaction may weaken U.S. reputation (apologies to Press & Mercer), or because inaction may weaken the sovereignty norm generally (apologies to Krasner).
Washington's response has been fairly well-calibrated to these possibilities, but I'll argue that one issue remains especially tricky as a result of the administration's choices.
So far, the Obama administration has avoided spiral dynamics by eschewing a military-heavy response. Yes, reconnaissance aircraft have been sent to Poland and Romania, but in general, allies have been assured without giving Moscow a pretext or causing genuine fear. My guess is that American diplomats have also been encouraging Kiev to show restraint, which the latter has certainly done.
Of course, there's a price to pay for steering clear of a spiral: the three other worrying possibilities above are tied to relative inaction. So what kind of pushback has there been? We've seen some targeted sanctions as well as condemnatory speech and symbolic punishment (such as kicking Russia out of the G8). Naming and shaming perpetuate the "organized hypocrisy" of sovereignty even if a more costly punishment isn't feasible.
What I want to draw attention to is an additional move that Obama has made to deter Russian expansion while simultaneously ameliorating the reputation issue. In public statements on March 25 and 26, the president drew a sharp distinction between NATO and non-NATO countries. At the Hague on the 25th, he warned, "What [NATO allies] are now doing is organizing even more intensively to make sure that we have contingency plans, and that every one of our NATO allies has assurances that we will act in their defense against any threats... When it comes to a potential military response, that is defined by NATO membership" (emphasis mine). The president clearly implied that no such response will be forthcoming for non-NATO countries, and noted pointedly the next day that Ukraine is not a member of the alliance.
I think this was more than just an attempt to draw a red line (cringe, sorry) for Putin along NATO borders. If we think reputation matters at all, we often think that the only way to protect it is to fight; inaction can only mean reputational damage. But Anne Sartori's book Deterrence by Diplomacy argues that leaders should value a reputation for honesty, not a reputation for resolve or toughness. Honesty makes future threats more believable while a reputation for bluffing over time has the opposite effect. Once we recognize this, we realize, as Sartori argues, that leaders who know they will not intervene in a given situation can burnish their reputation anyway by conceding before any threat is made--openly admitting that they have low resolve in the scenario at hand, then staying out militarily. This makes threats in other situations more meaningful by comparison.
Obama's statements seem to have followed this path because he has taken military intervention off the table outside of allied territory. Additionally, the U.S. gets to play up the value of its alliances in the process, the message being, "Sure, the Russians may have ignored American wishes in Crimea, but Ukraine was not a formal ally." Drawing the distinction between NATO and non-NATO countries in the Ukraine crisis, and stating openly that the latter are on their own in terms of armed defense, has thus helped the U.S. protect its reputation in East Asia, where, if Sartori is right, future deterrent threats on behalf of allies will be taken more seriously.
Still, the move is fraught with risk. Recalling Dean Acheson's "defensive perimeter" speech, the danger is that Putin is encouraged to aggrandize because he perceives that everywhere up to NATO's doorstep is his for the taking without armed opposition. What does the U.S. have to say about the small number of states in no-man's land? "Now, those countries--border countries that are outside of NATO--what we can do is what we’re doing with Ukraine, which is trying to make sure that there is sufficient international pressure and a spotlight shined on the situation in some of these countries, and that we’re also doing everything we can to bolster their economies, make sure that through various diplomatic and economic initiatives that they feel supported and that they know that we stand by them. But when it comes to a potential military response, that is defined by NATO membership..." It's not very clear what the solution is for these countries.
Overall, the U.S. has capably managed the crisis to date. But it is going to be difficult to deter Russia without reneging on the pledge not to use force should Putin begin to expand into the intermediate areas. Western countries will need to find a way to ramp up sanctions and other forms of pressure commensurate to Russian advances, preferably in a reversible way to make the off-ramp attractive. We know that many of these levers will be difficult to pull due to mutual dependence, so let's just hope that Putin has limited aims or that he decides that holding territory beyond "Russian-speaking" areas will be prohibitively costly regardless of Western reaction.
Update: A new report suggests that Gen. Philip Breedlove, NATO Supreme Allied Commander Europe, differs with the Obama administration on plans to defend the rest of Ukraine. He may have released satellite photos of Russian mobilization to draw more attention to the difficult issue of defending intermediate states.