Long sleeve t-shirts with good/pithy quotes on them… nothing dirty, just phrases or designs that extend your brand. Stuff that is 1: more than just your logo on a shirt and 2: worth the purchase. Oh, and 3: extends your brand.
Obviously t-shirts. Maybe with a US flag on the left sleeve (or something on the left sleeve; it always surprises me that companies don’t put things on the left sleeve… when I hang my arm out the window in the Summer, why not get free eyeballs on your logo/quote/flag)
Hats
Maybe a fleece?
All quality merch, good gear that people will want to wear. Tastefully designed so they will wear it.
(You’re probably set for designs but branding is my jam, and since you asked I thought I’d offer some thoughts)