Personally, I don't care where things are made - certainly don't care if they are made in the US or not - I am in the UK so its not unpatriotic of me not to buy US - I have currently 4 US made PRS...
As for apparel, things that are fully licenced by a 'brand' such as PRS, it makes much more sense to buy from the 'brand' themselves as it is supporting the brand. Buying 'unlicensed' but made in the US, is just supporting the person who is breaking the law by making it and the seller too rather than supporting the 'brand' you are advertising/promoting. Its better to buy a fully licensed, made in China PRS t-shirt or baseball cap than it is to buy a made in the US unlicensed copy.
At least that is my opinion. If you are just after US guitar themed Schwag that is not necessarily associated with a specific brand - like a US made generic guitar themed T-Shirt rather than a PRS specific branded Made in China (for example) T-shirt, then I can't help you. If you want to support and show your support of PRS (or any brand), then its better to buy those regardless of where they are made because fully licensed products are supporting these American brands - even if they are actually made outside of the US.
I can understand if that puts you into a difficult position between supporting an American Brand but wearing a 'made in China' (for example) T-Shirt or having to wear a 'generic' guitar themed made in the US that supports US manufacture but doesn't support a specific brand - at least not legally. As I said, I am in the UK so I really can't help you in sourcing US made options. I would assume you have known US brands, maybe Etsy could be a place to check for US crafters to make and sell musical/guitar themed items and apparel. Those that make PRSish themed items (closely resembling but different enough to not be copyrighted though could well be supporting US made but not supporting the US brand. That's where your loyalties may well be tested - whether its better to be US made but ripping off a US brand or to be made elsewhere but fully supporting the US brand...