dear every vocalist who has ever performed the national anthem of the united states in public,
it is the national anthem. it is not the hook for your next big hit, it is not your opportunity to make your mark on public events. you have been honored with the opportunity to perform this one small civic service. do not ornament, invent, or improvise the national anthem. just sing it. sing it the way it's written.
it's not a particularly good national anthem, but it's the one we've got.
nobody is here to hear you sing the anthem. everybody is here for the ballgame / pageant / parade / airshow / meeting. it is a simple civil duty and it is not your place to make the national anthem your own personal style statement. nobody is going to hear your imaginative rendition of the national anthem and run out and buy tickets to your next show or buy your new album.
just sing it, ok? just perform this small civil service without drawing too much attention to yourself or drawing it out for too long, bow politely and get off the stage.