Create map of the USA

Hi guys, I wanted to ask what might be the best approach to solve my current problem. Long story short, I want to have the USA as the map for my game. It does not need to be ultra high quality, I just need it to be "good enough". I tried using a heightmap from NASA, but even at 8k resolution, it looks like crap. So I thought that maybe I should use multiple heightmaps and terrain tiles. The questions are:

1. Is this a viable option or do you guys have something simpler in mind?

2. Assuming this approach can work, how can I possibly automate this process? Meaning downloading the different heightmap automatically, without seams and weird stitching problems, also to save time. If there is an asset that can do this, please point me to it, or service, anything.

Thx in advance, have a great day.