I love seeing the American flag. I dont think its disrespectful at all.
About the sticker on your truck thing, a kid at my school put a american flag sticker on his car, i dont have a problem with that at all since i have one on my truck. but the thing is, he put his upside down, i asked him if it was a mistake or he did it on purpose and he said "it looks cooler".Personally i think thats disrespectful putting it upside down.