Where got such thing as only US sets have the problem. Nowadays all electronics are made in China, same factories, same production process, same parts - it's the same quality for all regions. Unless it happens that in US the particular bluetooth frequency is used by some unique mobile devices or military frequency which interferes with the joycon, the same will happen in every country.
There's no explanation given yet, can't just assume the problem is on the joy con side and can easily replace it with color model. If your phone loses connection to your bluetooth earphone, it could be the earphone having weak bluetooth signal/range but it could also be the phone side having weak signal/range.