The first video is from the bridge section. Basically, you're swarmed with soldiers as they try to prevent you from crossing over into their warehouse.
This video is a section from the heli battle. Of COURSE you get to fight back against the heli. ;P This battle is great, and no matter how many times I play it (and I've played it a lot), it never stops being fun.
Don't forget, the levels featured in these videos are available RIGHT NOW. Hit the link and let me know what you think!