North Americans are too comfortable with just MAKING YOUR OWN MESS SOMEONE ELSE'S PROBLEM.
Just pick up your damn litter, for a start. Keep it in your pocket. Carry it to the trash can.
Secondly, don't take all of the disposable crap a store gives you! Take your own cup, your own cutlery. There are tiny ones that fit in your pocket or a bag.
Third, if you see a mess, make it your problem if reasonable. You can wash your hands afterward. North Americans seem to have a problem picking stuff up or holding on to it for 5 minutes because it's "icky". You just ate that ice cream cone, the package isn't any more icky yet than when you ate it. Put it in the trash.
BUT YES, THE ANSWER IS TO USE A MULTI-USE STRAW. They exist, they're simple to carry, and it's the responsible thing to do.