Completing bigger countries though is quite difficult in single trips and in a way it's a positive thing as you get to revisit special sites while visiting new omes.
I definitely agree with this sentiment. I will likely not complete my remaining sites in Germany, Italy, Spain, or France all in one visit, which will allow me the opportunity to go back and visit some of the cities and regions I've enjoyed from past trips. There are some countries I am fairly certain I will never complete because of the number of inscriptions, the level of activity, and the large geographic area between sites -- I'd put China and India in those categories (even though I still have yet to visit either). For other countries, I consider it a challenge to complete them (such as Canada, the U.K., and the U.S.), which makes trip planning fun.
The US is active these days, making the completeness check just a bit more challenging.
I'm glad to see that, and thanks for posting all the updates on the tentative list! I'm looking forward to seeing what the U.S. puts forward later this year. I'm glad a lot of the current U.S. World Heritage Sites are national parks, since I am also making it a point to visit as many of those as I can. That's one of the advantages you have to living out West! Incidentally, if you ever consider visiting Caribbean World Heritage Sites, there are some cruises that allow the opportunity to see between 4 and 5 sites on different islands, including La Fortaleza in San Juan. Similarly, many Alaska cruises offer trips to Glacier Bay (unfortunately I've been to Alaska twice and still haven't made it there, since I haven't gone on a cruise; I have been able to see some great sites across the state, though -- it's a beautiful place!).