There is a meme circulating in the media that by withdrawing support for a missile-defense shield based in the Czech Republic and Poland, Barack Obama is letting down our close allies in these two countries. But it is not quite clear who we are letting down. Yes, right-wing governments in both countries signed a treaty with the US to build missile launchers (in the case of Poland) and a radar system (in the Czech Republic). However in neither case was the treaty ratified by parliament and in both countries most of the left has opposed the missile shield.
More to the point, the public in both countries has been decidedly lukewarm about the treaty to put it mildly. Below is a graph of Czech public opinion showing that over the past three years, a nearly unchanged two-thirds of the public has been opposed to construction of the radar and an even higher percentage has desired a referendum on the issue (presumably in order to vote against it; the data used to construct the graph are available here.) And this despite considerable government propaganda and public antipathy towards Russia.
I don’t have similar data on Poland, but a poll from August 2008 (when the treaty was signed) showed that 56% of the public opposed the missiles and only 27% supported supported them. Support rose somewhat in October 2008 (after the Russia-Georgia crisis), but a majority still opposed the radar (46% to 41%). (See here for more details.)
In short, while we may be letting down some right-wing political elites in both countries who did go to the mat on this issue, we are emphatically not letting down the Czech and Polish people who have been skeptical and in fact fearful of the idea from the start.
UPDATE: More from Andrew, who subsequently tracked down a time series of Polish opposition to the missile deployment.
These data show somewhat less opposition than in the Czech Republic, but still a relatively consistent 60% of the public has been opposed to basing missiles in the country Opposition did drop somewhat after the Russia-Georgia crisis, but at the time of the treaty signing in August 2008, 67% of respondents were opposed. And bear in mind that Polish attitudes towards Russia are even more negative.