The 3% US growth is almost certainly primarily from Spanish-language congregations, and the growth there is almost entirely from recent 3rd-world immigrants (both JWs moving in and conversions from the 'field').
At an elders school I attended about 6 years ago, the comment was made that fully 25% of the JWs in the USA were in Spanish-language congregations. I'm virtually certain the percentage is significantly higher now.
Recent 3rd world immigrants don't move to the US and instantly become internet-savvy.
From my perspective the English language congregations are actually in decline in most areas.
The point about the internet is still valid - those exposed to the internet are far less likely to become, or remain, JWs.