There's been a lot of talk about high speed rail plans for parts of the US and there's a very useful map of the proposals on the Trains Magazine website. It includes the money allocated to each route. It's not very big but I've uploaded a rather better version through the link here:
Not all the routes are "high speed" in international terms. Some are simply upgrades to existing routes to give 90-110 mph running (the taupe coloured lines) and others are described as "new conventional service" (green routes) or "upgrades to conventional service" (blue routes). In international terms, true high speed for trains means normal capability to run at over 125 mph (200 km/h).
There's a series of articles on the High Speed Rail situation in the US in Trains Magazine.