1) I think its ok - and is the best of the bunch, but would be better if you cropped out the bird on the left.
2) Doesn't do too much for me - might benefit from a tighter crop as well.
3) Hmmm - not too much I can say - its a flag. But the first thing I thought was its backwards. I'm from Canada, so I may be naive, but I think I have only seen the US flag when its the other way! Maybe flip the image...
4) Not sure what you are taking a picture of here. The composition makes me think that the sky is the subject, but the building is much more interesting. Unfortunately, you can only see part of it.