First of all, it's not an "American Restaurant", it's a 100% Belgian place. And secondly, this place is so good I didn't even want to jinx it by leaving this tip.
Mussels with SpicyItalian Sausage, Peppers, Onions and Tomatoes was excellent although not quite as good as BrasserieBeck's. The Mussels St. Arnold's is still their stand-out dish.
Always ask what their specials are for the day. Normally their mussels special is only $10 instead of $12. Just as delicious and big enough portion for lunch :)
Husband is 41, I just turned 39 yesterday and they didn't serve us alcohol because we only had our Turkish ID's on us. Well at least we still don't look over 21! A big yay for it :)