A fun game against rommel, Armor vs Tank Destroyer. Im not very good with Americans, but this game was fun for sure. I made many mistakes, feel free to give me tips and tricks on how to improve.
In response to your question about how to deal with the Mortar HT - you could've used Elite Infantry in the form of Rangers/Paratroopers, stickies would've helped a lot to slow it down for you to finish with BAR fire. You could also have got an AT gun as the Mortar HT barely out-ranges an AT gun and you were dominating the infantry combat so he couldn't have pressured it.
When you did get AT guns you needed to be more aggressive with them and force him to back away instead of setting them up and giving him time to respond with the mortar.
Mostly you need to focus on knocking it out - if you'd actually done that one time when you rushed his forces it would've died very quickly.