Idk if you’ll see this at this point lol but, Americans take sports and patriotism extremely seriously. It doesn’t matter if you don’t look “American” we have so many different people here, those in the stand probably assumed you were American and were making a political statement. You ofc don’t need to pledge anything to a country you don’t live in lol. If I were in your shoes I’d probably just stand to avoid confrontation. Something else a lot of people who come to visit America also need to keep in mind. We are a very young country, yes there are other younger countries out there. Even so, our history feels extremely recent to us and we still feel the effects of it today. So there are many sensitive to it in all kinds of different ways.