VPNs protect your from geting caught torrenting, but it cant protect you from the US-goverment.
First of all most of the advertized VPN’s are Honeypots and/or back/bugdoored by the NSA.
And even if they where not…so much of the internet runs on servers/services/isp’s that are related to american companys that Timing attacks are possibe (for example your ISP logs and shared your encrypted traffic and the NSA then compares Timing patterns of requests with other services).