What a Greek exit means for the U.S.

May 29, 2012, 7:10 PM UTC

FORTUNE – A curious development happened last week in the ongoing euro zone crisis. Finance ministers from the 17 countries that use the euro agreed they needed to develop back-up plans in case debt-troubled Greece leaves the euro. The tone was unexpectedly bold, given that officials have mostly kept mum about a potential Greek exit to avoid panicking markets.

Investors have raised bets that Greece’s euro days are numbered. Now as Europeans try to prepare for what could possibly turn out to be a financial disaster, it’s hard not to wonder why there isn’t much talk about a U.S. contingency plan. More specifically, what might a Greek exit mean for the U.S.?

Next month, Greece will host elections that could potentially make or break its euro membership. Judging by U.S.-Greek trade and financial links, Greece alone may be too tiny to derail America’s economic recovery. And as Fortune’s Shawn Tully noted recently, a return to the drachma will instantly turn Greece into a dirt-cheap destination for Americans and vacationers around the globe.

MORE: Wake up, Europe! It’s time for a real fix.

As far as trade goes, Americans sell relatively little to Greeks. Only 0.1% of U.S. exports go to Greece and less than 3% go to the five peripheral euro zone countries combined, according to a research report by Capital Economics. Even if a Greek exit rattles markets across the wider euro zone, U.S. sales to the area wouldn’t pull down U.S. growth by much. Only 14% of exports are sent to the euro zone, so even a severe 5% fall in gross domestic product across the euro zone would only knock off 0.2 percentage points from U.S. growth in each of the next two years, according to Capital Economics economists Paul Ashworth and Paul Dales.

The projections might allay some fears, but economists acknowledge that bigger threats lie in the financial links between Greece and the U.S. The greatest concern is the uncertainty following Greece’s departure. If investors panic, triggering bank runs and a disorderly break-up of the euro that includes bigger debt-ridden countries like Spain or Italy, the crisis will almost certainly be felt across the U.S. financial system.

U.S. banks have been reducing their exposure to the euro zone’s peripheral countries to help ease that concern. Claims on Greece equal only 0.3% of U.S. banks’ core capital, according to Ashworth and Dales. And when it comes to the peripheral countries combined, claims by American banks make up a modest 12% of core capital.

Taking the wider euro zone into account, the risks become much bigger. U.S. banks’ exposure to the area is significant, making up about 60% of core capital. It was just last fall that the broker-dealer MF Global collapsed following big bets on euro zone debt.

MORE: Greece: The anatomy of a default

What’s more, 20% of all loans made in the U.S. come from European banks, which own sizeable amounts of Spanish and Portugese debts. If Greece’s exit instigates a big sell-off of such debts, for instance, it could certainly crimp European banks’ willingness to lend.

“The credit spigot in the U.S. could tighten again,” says Mark Zandi, chief economist of Moody’s Analytics. And because Europe is China’s biggest export market, a significant slowdown in the Chinese economy could likely pull back growth in the U.S. and the rest of the world.

Indeed, there are several ways the dominos could fall. And as Europeans talk about contingency plans,what might the U.S. do?