As Stoked said you can request the bassinet but preference will be given to smaller children. Some airlines are very strict as well and will not allow older children in the bassinet.
I did one trip to Germany once with my P&T Explorer, I had a travel bag for it which makes the pram look so much smaller and compact and it wasn't a problem. But again it will depend on the airline.
To go through security, you will be asked to empty everything out of your pram and they will manually search it.
I have travelled by myself each time and found a carrier not very practical as it was just too much to carry - baby and hand luggage so a smaller stroller has worked better for me. But if it's two of you you might be ok with a carrier.
You can take baby food, but like Stoked said I am not sure about guidelines to the USA. I have travelled via Canada and they where fine. The airlines also have jars on board.
I am about to fly to Germany for the 4th time with my 2 year old. So far I have always had good experiences and found airport and airline staff very helpful. I generally make sure to check in quite early and will ask during check in to have an extra seat blocked off. Then I ask again as soon as I get on the plane and so far have always been successful with this.
I regards to seating - the rows with the bassinet have extra leg room which is nice, however the armrest between the seats can not be lifted as the table and TV are stored in it. Something to consider if you don't get or end up using the bassinet. I prefer them to be lifted so my daughter can lay down to sleep.
I also try to avoid these rows as I sometimes find other children who may be unsettled make it more difficult for my child to sleep.
Sorry for the long post. Hope this helps though!