There are easier ways to make yourself more visible to drivers. Hi-viz clothing and even helmets are becoming more common, and a variety of retro-reflective stickers can be found in most shops.
Patriotism can be displayed in the form of a simple patch for your hi-viz jacket, or with one of the aforementioned reflective stickers in the form of a flag.
Brand loyalty can also be shared with those around you in the form of patches and stickers, unless you ride a BMW in which case their lawyers will go after you for infringing on their trademark unless you purchase the logo directly from them for three times the going street price.
If you are worried that the electrical generating capacity of your bike is insufficient and needs to be supplemented by tapping into overhead wires as you pass beneath, Honda and BMW both have bikes with enough amperage generated to toast your gonads.
If the flagpole is needed to hang freshly washed clothing out to dry, Helen2Wheels makes mesh bags that flap in the breeze and do a pretty good job of drying things as you ride.
If there are other uses for flagpoles, please elaborate.