The only users of WeChat have strong ties to China, and use it for those ties (e.g. WePay). Even in HK and Taiwan, WeChat is not used outside of those reasons.
WeChat working in the US is like UnionPay working in the US. Ya, its great if you are a Chinese tourist or an expat with a Chinese bank account, but it is irrelevant if you aren't, UnionPay isn't going to start taking over the American ATM card market.