http://www.cnn.com/2014/06/20/us/vietnam-war-five-things/

Do you think if we'd hadn't been involved beginning with Eisenhower, Kennedy would have still gone into Vietnam?  

If you're only using the declared wars, you need to take off all that followed world war 2. World war 2 was the last war that we actually declared it a war. If we get to use undeclared wars then you need to add quite a few other countries we've invaded but didn't call them wars. 
http://www.senate.gov/pagelayout/history/h_multi_sections_and_teasers/WarDeclarationsbyCongress.htm