According to Ukrainian media [Update: now picked up with a wire report from Reuters], Ukraine is pulling out of its scheduled friendly with the US, which previously had been moved out of the country to Cyprus due to instability in the country. That instability has now been overtaken by a Russian invasion of the Crimean peninsula.
There's no word yet on the impact to the US National Team. It's hard to imagine a replacement opponent being lined up this quickly, so the most likely outcomes are an impromptu training camp in Cyprus for a few days or a total cancelation. The latter would free Clint Dempsey to return to the Sounders earlier. He still might not start, given that he's yet to train with the Sounders this preseason, but it's a possibility. And even if he doesn't, he'd likely be available for more minutes without a midweek match for the national team.