I agree with Jim in this case for several reasons, but with one caveat. Using the same VFD for both machines using the same parameters is not a good choice. What can be done is some VFDs allow you to setup two separate parameter files, one for each motor, you can switch the motor parameter files based on a programmed input. You cannot use the machine motor switch/contactors to control the VFD output, you need to program the VFD low voltage inputs for the VFD run commands. Since the run commands and mode of operation would be different between the lathe and the mill, it can get messy quickly. At the end of the day if this is a long term replacement you would be better off using a dedicated VFD for each machine. Something like the 2 Hp Teco L510 ($175) on the mill, or better yet a GS3, WJ200 or other mid priced VFD would be better suited for the lathe. The Teco L510 cannot accommodate an external braking resistor which is a requirement on a lathe in particular of that size.
If you are looking for a drop in fixed 60 Hz single phase to 3 phase system, there is the Phase Perfect converters, but they are very expensive, so more practical for powering multiple machine or CNC machines.
I am not sure if any VFDs are American made, and most of the components will be offshore, although you can go with a US brand like ABB which have a good reputation. I mostly install/work with the Hitachi WJ200 and the Yaskawa V1000 series. Both are widely used, along with the Automation Direct (GS3), and probably have better support for these brands from others in this forum. Automation Direct is a great US company and very good technical support. At the end of the day, if you want just a plug and play solution and do not need the VFD features, it is probably both more practical and cost effective to get/build a 5 or 7.5 Hp replacement RPC.